ZeroStack Corp. (ZSTK) insider Michael Heinrich discloses 30.2% stake

Rhea-AI Filing Summary

ZeroStack Corp. shareholder Michael Heinrich reports beneficial ownership of 5,579,783 common shares, with sole voting and dispositive power over this stake. This represents 30.2% of the outstanding common shares on a partially-diluted basis, based on 17,489,828 issuer shares outstanding as of July 20, 2026.

Zero Gravity Labs Inc., a Delaware corporation owned and controlled by Heinrich, is a joint reporting person and reports a beneficial stake representing 26.4% of the class. Heinrich serves as Chief Executive Officer of Zero Gravity Labs Inc. and is a director and Chairman of the Board of ZeroStack Corp. as of September 20, 2025. The report references a Joint Filing Agreement dated April 2, 2026 and a Form of Stock Option Agreement dated May 5, 2026, both incorporated by reference.

Filing Explained

The amendment leaves the affiliate’s exact holding and the economics or purpose of any stake change unresolved.

As a Schedule 13D amendment, the filing tracks changes in a holder's stake or stated intent. Its Zero Gravity Labs section is internally inconsistent: it lists 4,608,575 shares with shared voting and dispositive power but 4,607,575 as the aggregate amount, so the affiliate's exact reported holding cannot be stated from this filing alone.

The filing leaves Item 3, covering source and amount of funds or other consideration, and Item 4, covering transaction purpose, blank. It therefore does not establish the consideration, funding, or purpose behind any change in the reported stake.

Key Figures

Beneficial ownership – Michael Heinrich: 5,579,783 common shares Ownership percentage – Michael Heinrich: 30.2 % Shares outstanding: 17,489,828 shares +2 more

5 metrics

Beneficial ownership – Michael Heinrich 5,579,783 common shares Sole voting and dispositive power; reported stake in ZeroStack Corp.

Ownership percentage – Michael Heinrich 30.2 % Portion of ZeroStack common shares on a partially-diluted basis as of July 20, 2026

Shares outstanding 17,489,828 shares ZeroStack issuer shares outstanding as of July 20, 2026 used for ownership calculations

Ownership percentage – Zero Gravity Labs Inc. 26.4 % Percent of ZeroStack common shares represented by Zero Gravity Labs Inc.’s beneficial stake

Event date 07/20/2026 Date of event giving rise to the reported beneficial ownership

Key Terms

beneficially owned, sole voting power, dispositive power, partially-diluted basis, +1 more

5 terms

beneficially owned regulatory

"Aggregate amount beneficially owned by each reporting person"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole voting power regulatory

"Number of Shares Beneficially Owned by Each Reporting Person With: sole voting power"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

dispositive power regulatory

"Number of Shares Beneficially Owned by Each Reporting Person With: sole dispositive power"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

partially-diluted basis regulatory

"has been calculated on a partially-diluted basis"

A partially-diluted basis is a way of counting a company’s shares that includes currently outstanding shares plus certain likely additional shares from things like vested options, warrants, and convertible securities, but excludes more speculative or unissued items. For investors it gives a more realistic view of ownership stakes and per-share figures — like earnings per share — by showing dilution that is probable today, much as counting people with purchased tickets (but not those who might buy later) gives a clearer sense of how full a theater really is.

Joint Filing Agreement regulatory

"Joint Filing Agreement dated April 2, 2026"

AI-generated analysis. How Rhea-AI works. Not financial advice.

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

Available on EDGAR 07/21/2026 - 04:57 PM Accepted by SEC EDGAR 07/21/2026 - 04:56 PM Learn about SEC filing dates

FAQ

How many ZeroStack Corp. (ZSTK) shares does Michael Heinrich report owning?

Michael Heinrich reports beneficial ownership of 5,579,783 ZeroStack Corp. common shares. He has sole voting and dispositive power over this stake, which represents 30.2% of the outstanding common shares on a partially-diluted basis.

What percentage of ZeroStack Corp. (ZSTK) does Zero Gravity Labs Inc. report owning?

Zero Gravity Labs Inc. reports a beneficial stake representing 26.4% of ZeroStack Corp.’s common shares. The stake is reported with shared voting and dispositive power and is calculated using the same outstanding share count referenced in the ownership disclosure.

What is the total number of ZeroStack Corp. (ZSTK) shares outstanding referenced in this Schedule 13D/A?

The ownership calculations are based on 17,489,828 ZeroStack Corp. shares outstanding as of July 20, 2026. The 30.2% stake reported by Michael Heinrich is explicitly described as being calculated on a partially-diluted basis using this share count.

What roles does Michael Heinrich hold at ZeroStack Corp. (ZSTK) and Zero Gravity Labs Inc.?

Michael Heinrich is the Chief Executive Officer of Zero Gravity Labs Inc. and, as of September 20, 2025, also serves as a director and Chairman of the Board of ZeroStack Corp.. These roles are disclosed in the identity and background section.

What key agreements related to ZeroStack Corp. (ZSTK) securities are referenced in this filing?

The disclosure references a Joint Filing Agreement dated April 2, 2026 and a Form of Stock Option Agreement dated May 5, 2026. Both documents are incorporated by reference from earlier SEC submissions related to ZeroStack and the reporting persons.

When did the ownership event occur that triggered this Schedule 13D/A for ZeroStack Corp. (ZSTK)?

The event requiring this ownership disclosure is dated July 20, 2026. Ownership percentages, including Michael Heinrich’s 30.2% stake and the 26.4% stake reported by Zero Gravity Labs Inc., are calculated using issuer share data as of that date.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 3)

ZeroStack Corp.

(Name of Issuer)

Common Shares, no par value

(Title of Class of Securities)

98956L101

(CUSIP Number)

Richard Raymer
Dorsey & Whitney LLP, 66 Wellington St. W., Suite 3400
Toronto, A6, M5K 1E6
(416) 367-7370

Michael Heinrich
Zero Gravity Labs Inc., 548 Market Street, PMB 33721
San Francisco, CA, 94104
(416) 861-2267

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

07/20/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 98956L101

1

Name of reporting person

Heinrich Michael

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 5,579,783.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 5,579,783.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

5,579,783.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

30.2 %

14

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person:

Percentage of class is based on 17,489,828 outstanding Issuer shares as of July 20, 2026, and has been calculated on a partially-diluted basis.

SCHEDULE 13D

CUSIP Number(s): 98956L101

1

Name of reporting person

Zero Gravity Labs Inc.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 4,608,575.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 4,608,575.00

11

Aggregate amount beneficially owned by each reporting person

4,607,575.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

26.4 %

14

Type of Reporting Person (See Instructions)

CO

Comment for Type of Reporting Person:

Percentage of class is based on 17,489,828 outstanding Issuer shares as of July 20, 2026.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Shares, no par value
(b)	Name of Issuer: ZeroStack Corp.
(c)	Address of Issuer's Principal Executive Offices: 2626 Cole Avenue, Suite 300, Dallas, TEXAS , 75204.
Item 2.	Identity and Background
(a)	i) Michael Heinrich (the "Reporting Person") ii) Zero Gravity Labs Inc., a Delaware corporation owned and controlled by the Reporting Person ("0G")
(b)	i) and ii) 548 Market Street, PMB 33721, San Francisco, CA 94104
(c)	The present occupation of the Reporting Person is Chief Executive Officer of 0G, 548 Market Street, PMB 33721, San Francisco, CA 94104. The Reporting Person is also a director and the Chairman of the Board of the Issuer as of September 20, 2025.
(d)	The Reporting Person and 0G have not, during the last five years, been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).
(e)	The Reporting Person and 0G have not, during the last five years, been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction, and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws, or finding any violation with respect to such laws.
(f)	i) United States ii) Delaware
Item 3.	Source and Amount of Funds or Other Consideration
	i) and ii) OO
Item 4.	Purpose of Transaction
	.
Item 5.	Interest in Securities of the Issuer
(a)	5,579,783 COMMON SHARES 30.2%
(b)	i) 5,579,783 total sole voting and dispositive authority; 0 total shared voting and dispositive authority; Total Shares: 5,579,783; Percentage - 30.2% ii) 0 sole voting and dispositive authority: 4,608,575 shared voting and dispositive authority; Total Shares: 4,608,575; Percentage - 26.4%
(c)	See Item 4
(d)	Not applicable
(e)	Not applicable
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Joint Filing Agreement dated April 2, 2026 Form of Stock Option Agreement dated May 5, 2026
Item 7.	Material to be Filed as Exhibits.
	Exhibit 99.1 to Schedule 13D Amendment 2 filed with the Securities and Exchange Commission on April 2, 2026, is incorporated by reference herein Exhibit 10.1 to the Issuer's 8-K filed with the Securities and Exchange Commission on May 6, 2026, is incorporated by reference herein

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Heinrich Michael

Signature:	Michael Heinrich
Name/Title:	Reporting Person
Date:	07/21/2026

Zero Gravity Labs Inc.

Signature:	Michael Heinrich
Name/Title:	Director of Zero Gravity Labs Inc.
Date:	07/21/2026