Not Able to delete private azure dns zone even if there is no nested link

**Describe the bug**
Cannot delete private dns zone even if there are no nested links

**To Reproduce**
create global zone and try to delete

**Expected behavior**
zone should be deleted , if there is no nested resources in it.

**Environment summary**
PS C:\Users\digeler> az network private-dns zone show -n documents.azure.com -g polydgeuse1
{
"etag": "a69969af-60b0-4490-8059-1906c48b48c9",
"id": "/subscriptions/a9f4e502-9188-4e9c-857f-532dd66f5d0c/resourceGroups/polydgeuse1/providers/Microsoft.Network/privateDnsZones/documents.azure.com",
"location": "global",
"maxNumberOfRecordSets": 25000,
"maxNumberOfVirtualNetworkLinks": 1000,
"maxNumberOfVirtualNetworkLinksWithRegistration": 100,
"name": "documents.azure.com",
"numberOfRecordSets": 1,
"numberOfVirtualNetworkLinks": 0,
"numberOfVirtualNetworkLinksWithRegistration": 0,
"provisioningState": "Succeeded",
"resourceGroup": "polydgeuse1",
"tags": null,
"type": "Microsoft.Network/privateDnsZones"
}

rllib3.connectionpool : https://management.azure.com:443 "DELETE /subscriptions/a9f4e502-9188-4e9c-857f-532dd66f5d0c/resourceGroups/polydgeuse1/providers/Microsoft.Network/privateDnsZones/documents.azure.com?api-version=2018-09-01 HTTP/1.1" 409 114
msrest.http_logger : Response status: 409
msrest.http_logger : Response headers:
msrest.http_logger : 'Cache-Control': 'no-cache'
msrest.http_logger : 'Pragma': 'no-cache'
msrest.http_logger : 'Content-Length': '114'
msrest.http_logger : 'Content-Type': 'application/json; charset=utf-8'
msrest.http_logger : 'Expires': '-1'
msrest.http_logger : 'x-ms-failure-cause': 'gateway'
msrest.http_logger : 'x-ms-request-id': '92920106-a73e-461a-8dd0-e320966bcdc5'
msrest.http_logger : 'x-ms-correlation-request-id': '92920106-a73e-461a-8dd0-e320966bcdc5'
msrest.http_logger : 'x-ms-routing-request-id': 'GERMANYWESTCENTRAL:20200901T100854Z:92920106-a73e-461a-8dd0-e320966bcdc5'
msrest.http_logger : 'Strict-Transport-Security': 'max-age=31536000; includeSubDomains'
msrest.http_logger : 'X-Content-Type-Options': 'nosniff'
msrest.http_logger : 'Date': 'Tue, 01 Sep 2020 10:08:54 GMT'
msrest.http_logger : Response content:
msrest.http_logger : {"error":{"code":"CannotDeleteResource","message":"Can not delete resource before nested resources are deleted."}}
msrest.exceptions : Can not delete resource before nested resources are deleted.
cli.azure.cli.core.util : Can not delete resource before nested resources are deleted.
Can not delete resource before nested resources are deleted.