I'm in the process of testing ZMM for deployment. We have a single GMS 2.1 server and have a second one running waiting for boarding. GMS A is populated using an LDAP group for users with large attachments. GMS B will be a vanilla config also using LDAP for provisioning. We may need a third GMS in the future.
At one time, GMS was to incorporate a redirector to point users to the correct GMS server, similar to the POAs.

How can I configure ZMM to enroll and configure the user if they are already provisioned on either GMS (or future 3rd GMS) with the same set of enrollment instructions-

server address

So far, ZMM has not allowed me to assign an LDAP server to multiple Activesync servers. Also, it seems Activesync servers can't service the same activesync domain.