feat(ec2-alpha): support availability zone id in SubnetV2

packages/@aws-cdk/aws-ec2-alpha/README.md

@@ -63,6 +63,31 @@ new SubnetV2(this, 'subnetA', {
 })
 ```
 
+### Availability Zone Specification
+
+SubnetV2 supports two ways to specify the availability zone:
+
+1. **Availability Zone Name** (`availabilityZone`): Standard AZ name like 'us-east-1a'
+2. **Availability Zone ID** (`availabilityZoneId`): AZ ID like 'use1-az1' for cross-account consistency
+
+**When to use AZ IDs**: Use `availabilityZoneId` when you need consistent placement across AWS accounts, as AZ names can map to different physical zones per account, but AZ IDs remain consistent.
+
+**Important**: AZ IDs are account-specific. The same AZ ID (e.g., 'use1-az1') may not exist in all accounts.
+
+```ts
+const myVpc = new VpcV2(this, 'MyVpc', {
+  primaryAddressBlock: IpAddresses.ipv4('10.0.0.0/16'),
+});
+
+// Using AZ ID for cross-account consistency
+new SubnetV2(this, 'CrossAccountSubnet', {
+  vpc: myVpc,
+  availabilityZoneId: 'use1-az1',
+  ipv4CidrBlock: new IpCidr('10.0.1.0/24'),
+  subnetType: SubnetType.PUBLIC,
+})
+```
+
 Since `VpcV2` does not create subnets automatically, users have full control over IP addresses allocation across subnets.
 
 ## IP Addresses Management

packages/@aws-cdk/aws-ec2-alpha/lib/subnet-v2.ts

@@ -62,8 +62,21 @@ export interface SubnetV2Props {
 
   /**
    * Custom AZ for the subnet
+   *
+   * Either `availabilityZone` or `availabilityZoneId` must be specified, but not both.
+   *
+   * @default - No availability zone specified, must provide availabilityZoneId instead
    */
-  readonly availabilityZone: string;
+  readonly availabilityZone?: string;
+
+  /**
+   * The AZ ID of the subnet
+   *
+   * Either `availabilityZone` or `availabilityZoneId` must be specified, but not both.
+   *
+   * @default - No availability zone ID specified, must provide availabilityZone instead
+   */
+  readonly availabilityZoneId?: string;
 
   /**
    * Custom Route for subnet
@@ -270,6 +283,14 @@ export class SubnetV2 extends Resource implements ISubnetV2 {
     // Enhanced CDK Analytics Telemetry
     addConstructMetadata(this, props);
 
+    // Validate availability zone specification
+    if (!props.availabilityZone && !props.availabilityZoneId) {
+      throw new UnscopedValidationError('Either availabilityZone or availabilityZoneId must be specified');
+    }
+    if (props.availabilityZone && props.availabilityZoneId) {
+      throw new UnscopedValidationError('Cannot specify both availabilityZone and availabilityZoneId. Use either availabilityZone or availabilityZoneId');
+    }
+
     const ipv4CidrBlock = props.ipv4CidrBlock.cidr;
     const ipv6CidrBlock = props.ipv6CidrBlock?.cidr;
 
@@ -307,6 +328,7 @@ export class SubnetV2 extends Resource implements ISubnetV2 {
       cidrBlock: ipv4CidrBlock,
       ipv6CidrBlock: ipv6CidrBlock,
       availabilityZone: props.availabilityZone,
+      availabilityZoneId: props.availabilityZoneId,
       assignIpv6AddressOnCreation: props.assignIpv6AddressOnCreation,
       mapPublicIpOnLaunch: props.mapPublicIpOnLaunch,
     });
@@ -315,7 +337,7 @@ export class SubnetV2 extends Resource implements ISubnetV2 {
     this.ipv4CidrBlock = props.ipv4CidrBlock.cidr;
     this.ipv6CidrBlock = props.ipv6CidrBlock?.cidr;
     this.subnetId = subnet.ref;
-    this.availabilityZone = props.availabilityZone;
+    this.availabilityZone = props.availabilityZone || subnet.attrAvailabilityZone;
 
     this._networkAcl = NetworkAcl.fromNetworkAclId(this, 'Acl', subnet.attrNetworkAclAssociationId);
 
@@ -395,6 +417,13 @@ export interface SubnetV2Attributes {
    */
   readonly availabilityZone: string;
 
+  /**
+   * The AZ ID of the subnet
+   *
+   * @default - No AZ ID information
+   */
+  readonly availabilityZoneId?: string;
+
   /**
    * The IPv4 CIDR block associated with the subnet
    *