if we rebuild vcenter servers on source and target sides, so that we can change the vcenters server fqdns, would we have to also rebuild the ZVMs? should we be able to export the vpgs and then import them without having to start over from total scratch?
Mike from Zerto here. If you are rebuilding vCenters, are you preserving the vCenter databases? Zerto relies on the MoRef IDs in the vCenter database to keep track of the vCenter components. If you do not preserve the vCenter database when upgrading/migrating/rebuilding vCenter, all of the MoRef IDs get changed, causing Zerto to lose track of everything in vCenter, and at that point, Zerto would need to be completely rebuilt.
Please see the following article for more information:
What we would recommend if to just rename the pre-existing vCenter installs, if that is possible, then running a Reconfigure on each of your ZVMs to account for the FQDN change. That way, your current replication is not affected.