Cannot create ROSANetwork when specifying the availabilityZones

[serngawy]

/kind bug

What steps did you take and what happened:
Creating ROSANetwork with setting the availability zones cause below error , also setting 3 availabilityZones however the availabilityZoneCount is 1

apiVersion: infrastructure.cluster.x-k8s.io/v1beta2
kind: ROSANetwork
metadata:
  finalizers:
  - rosanetwork.infrastructure.cluster.x-k8s.io
  name: rosa-net
  namespace: ns-rosa-hcp
spec:
  availabilityZoneCount: 1
  availabilityZones:
  - us-west-2b
  - us-west-2a
  - us-west-2d
  cidrBlock: 10.0.0.0/16
  identityRef:
    kind: AWSClusterControllerIdentity
    name: default
  region: us-west-2
  stackName: rosa-hcp-vpc
status:
  conditions:
  - lastTransitionTime: "2025-10-20T19:55:28Z"
    message: 'operation error CloudFormation: CreateStack, https response error StatusCode:
      400, RequestID: 982fcbb8-3615-4c6e-9f25-b1189771c818, api error ValidationError:
      Parameters: [AZ0] do not exist in the template'
    reason: Failed
    severity: Error
    status: "False"
    type: ROSANetworkReady

What did you expect to happen:

We expect to be able to create ROSANetwork

Anything else you would like to add:
Logs from capa pod

I1020 19:56:02.922678       1 rosanetwork_controller.go:129] "Reconciling ROSANetwork" controller="rosanetwork" controllerGroup="infrastructure.cluster.x-k8s.io" controllerKind="ROSANetwork" ROSANetwork="ns-rosa-hcp/rosa-net" namespace="ns-rosa-hcp" name="rosa-net" reconcileID="ab2c4d4d-43f0-425f-8f77-c93a4de616dc"
E1020 19:56:03.123266       1 controller.go:347] "Reconciler error" err="failed to start CF stack creation: operation error CloudFormation: CreateStack, https response error StatusCode: 400, RequestID: 86dc9f2b-5351-45b6-93ad-694a56d8a453, api error ValidationError: Parameters: [AZ0] do not exist in the template" controller="rosanetwork" controllerGroup="infrastructure.cluster.x-k8s.io" controllerKind="ROSANetwork" ROSANetwork="ns-rosa-hcp/rosa-net" namespace="ns-rosa-hcp" name="rosa-net" reconcileID="ab2c4d4d-43f0-425f-8f77-c93a4de616dc"

Environment:

• Cluster-api-provider-aws version: v2.9.2
• Kubernetes version: (use kubectl version): v1.29.14
• OS (e.g. from /etc/os-release):

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