ZPA - for M & A - Use case discussion

I have use case as follow:
Background:
Company A and Company B is merged. - Look for a easy allow company A to access a company B internal apps & resource via Zscaler.
Company A - Not Z-Scaler customer, Cloud IdP - Okta for their cloud applications.
Company B - Z-Scaler with ZPA for "internal resource | application access & ZIA for the Web-Proxy. ADFS as IdP- implemented.

Case Requirements
Company A users need to access Company B internal applications (Private Access) when they are needed - without interrupting company A access. (still use company A web-proxy for internet traffic, company A own exist client VPN solution to access Company B’s internal resource…)

Please let me you if someone out there had this use case and successfully implemented a working solution.

Thanks,

Bing

This sounds like a pretty standard ZPA use-case.
Create accounts in Company B for Company A users.
Give Company A users ZApp client with only ZPA enabled and create appropriate Application Segments and Access Policy.

Why we can not use company A’s IdP for authentication (via SAML)?
Avoid to create duplicated users accounts in both Active Directory is one of the main reason - look at Zscaler.