On the Amazon Web Services (AWS) Cloud, an Availability Zone has a name that can vary between your AWS accounts and an Availability Zone ID (AZ ID) that identifies its location. If you use AWS CloudFormation to create virtual private clouds (VPCs), you must specify the Availability Zone's name or ID when creating the subnets. If you create VPCs in multiple accounts, the Availability Zone name is randomized, which means that subnets use different Availability Zones in each account.
To use the same Availability Zone across your accounts, you must map the Availability Zone name in each account to the same AZ ID. For example, the following diagram shows that the use1-az6 AZ ID is named us-east-1a in AWS account A and us-east-1c in AWS account Z.
