Can I Change the AZ for an Instance?

No.

To use a different AZ, create another instance in the desired AZ, and then migrate data and switch IP addresses. For details, see Online Migration Between Instances.

Multi-replica cluster instances (whose master and standby nodes are) in a single AZ can be deployed across AZs by migrating the standby nodes to other AZs. For details, see Changing Cluster DCS Instances to be Across AZs.

For a basic edition master/standby instance, the AZ of its standby node can be changed by adding or deleting replicas. The AZ of an added replica can be specified as shown in the following figure. To add and delete replicas, see Modifying DCS Instance Specifications.