I heard back from support on this and it appears to be a relatively simple operation with minimal impact to Zerto:
Per support:
You will need use the Zerto Diagnostics utility(can be found in the ZVM machine) and select to reconfigure the connection with vCenter. In the wizard, enter the new IP and finish it through. The service will be restarted so wait a few minutes before login in to the ZVM again.
If you only intend to change the vCenter IP, the only downtime will be until you run the reconfigure (which will be very short and will not cause any notable impact).
Sam N.
