Undo admin takeover of domain

Question

Hi. Can i somehow undo internal admin takeover of domain .xyz and then make force admin takeover from existing tenant?

Details:
2 companys are merged. both just start using Power bi.
We have tenant "A" with domain .abc . Azure AD is NOT synced to on-premise AD.

I create user in .xyz domain and force internal admin takeover to check for subscriptions for sharepoint and skyp for business (there is no one)

Now i need to force admin takeover of domain .xyz in tenant A.
Best case scenario is to undu internal admin takeover if it possible.
If not, what should i do to migrate users.xyz and domain .xyz from tenant B to tenant A?