How can I map two different UPN Domains to the same new UPN Domain in Entra SCIM Provisioning?

I have a customer with two domains (hq.company.com and associates.hq.company.com). I need both of those domains to map to a new subdomain (test.hq.company.com) so that users from either domain can use their normal credentials to log into the new domain's resources. What is the best way to do this? I have tried multiple IIF statements, and using Replace() with an "or" or the "|" pipe operator, which don't seem to work.