This is Vladimir M with Zerto Support.
If you’re protecting an active-active cluster and only 1 server is failed over, then it should look for the second node, and when there is not a second node existing, the service won’t start. That’s the reason why active-active cluster is not supported by Zerto.
When you protect an active-passive cluster and when the primary node is failed over, it won’t look for the second node because the second node is supposed to be passive. The cluster service should start.
As Zerto only protects the primary node in an active-passive cluster, If you need to make the cluster work again, you need to create a new VM to build up a new cluster.