Does moving RDS to a different VPC change the AZ?

Moving an Amazon RDS instance to a different VPC within the same AWS account does not necessarily change the Availability Zone (AZ) of the instance. However, it's important to note that when moving an RDS instance to a new VPC, you need to ensure that the target VPC has subnets in the same AZ as your current RDS instance.

When modifying the DB instance to use a new DB subnet group in the target VPC, you should select a subnet group that includes subnets in the same AZ as your current instance. If the target VPC doesn't have subnets in the same AZ, you'll need to add them to the DB subnet group before moving the instance.

It's worth noting that while the AZ doesn't change by default when moving to a new VPC, you have the option to change the AZ during this process if desired. This can be done by selecting a different AZ when modifying the DB instance, provided that the target VPC has subnets in the desired AZ.

Remember that changing the AZ of an RDS instance can have implications for your application's connectivity and performance, so it should be done carefully and with proper planning.
Sources
Updating the VPC for a DB instance - Amazon Relational Database Service
Migrate an Amazon RDS for Oracle DB instance to another VPC - AWS Prescriptive Guidance
Migrate an Amazon RDS DB instance to another VPC or account - AWS Prescriptive Guidance