Hey @srivathsangk,
Thank you for reaching out to the Zoom Developer Forum.
For scenario 1, the parent organization - or account owner - would be responsible for the billing. If you wanted to set up a reseller structure where you could bill sub-account independently I recommend talking with our ISV Team.
This behavior is true for scenario 2 as well. Part of adding a user to your account means that you are responsible for their billing.
I’m not positive why this isn’t available via API but I know that it’s intended. If you would like to see this changed, I recommend posting in the #feature-requests category.
Thanks,
Max