Incompatible US EU customer accounts

Incompatible US EU customer accounts

Hello,
A few days ago, I migrated my company's account from DC US to DC EU. Following this migration I have many problems.
For example, I had several external clients who had access to projects on Zoho Projects. I tried to invite them but the support tells me that you can't invite a DC US user to a DC EU account.

The problem is that this user cannot recreate an account with his email address on Zoho.eu

I am told that each customer must request the migration of their account to DC EU. Do you have another solution? Because it's complicated to ask hundreds of customers to request a migration from Zoho!
Thanks