update zone sync docs to describe the functionality (#7479)

Author: pdabelf5

site/content/configuration/global-configuration/configmap-resource.md

@@ -182,11 +182,7 @@ For more information, view the [VirtualServer and VirtualServerRoute resources](
 
 ### Zone Sync
 
-{{< note >}} 
-If you previously installed OIDC or used `zone_sync` in the stream-snippets in [v4.0.1](https://github.com/nginx/kubernetes-ingress/tree/v4.0.1) or earlier, and you plan to enable the `zone-sync` ConfigMap key, please remove `zone_sync` from the old [stream-snippets](https://github.com/nginx/kubernetes-ingress/blob/v4.0.1/examples/custom-resources/oidc/nginx-config.yaml#L7) Otherwise, NGINX Plus will encounter duplicate directive error `[emerg] 13#13: "zone_sync" directive is duplicate in /etc/nginx/nginx.conf:164`.
-Once upgraded, remove the [old headless service](https://github.com/nginx/kubernetes-ingress/blob/v4.0.1/examples/custom-resources/oidc/nginx-ingress-headless.yaml) deployed for OIDC.
-{{< /note >}} 
-
+Zone Sync enables the [ngx_stream_zone_sync_module](https://nginx.org/en/docs/stream/ngx_stream_zone_sync_module.html) in NGINX Ingress Controller when NGINX Plus is used.  Multiple replicas are required to effectively utililise this functionality.  See the [zone sync documentation for further details](https://docs.nginx.com/nginx/admin-guide/high-availability/zone_sync_details/).
 
 {{<bootstrap-table "table table-striped table-bordered table-responsive">}}
 |ConfigMap Key | Description | Default | Example |
@@ -198,6 +194,11 @@ Once upgraded, remove the [old headless service](https://github.com/nginx/kubern
 |*zone-sync-resolver-valid* | Configures an [NGINX time](https://nginx.org/en/docs/syntax.html) that the optional [resolver](https://nginx.org/en/docs/http/ngx_http_core_module.html#resolver) directive for zone-sync will override the TTL value of responses from nameservers with. NGINX Plus & `zone-sync` Required | `5s` |  |
 {{</bootstrap-table>}}
 
+{{< note >}} 
+If you previously installed OIDC or used `zone_sync` in the stream-snippets in [v4.0.1](https://github.com/nginx/kubernetes-ingress/tree/v4.0.1) or earlier, and you plan to enable the `zone-sync` ConfigMap key, please remove `zone_sync` from the old [stream-snippets](https://github.com/nginx/kubernetes-ingress/blob/v4.0.1/examples/custom-resources/oidc/nginx-config.yaml#L7).  Otherwise, NGINX Plus will encounter duplicate directive error `[emerg] 13#13: "zone_sync" directive is duplicate in /etc/nginx/nginx.conf:164`.
+Once upgraded, remove the [old headless service](https://github.com/nginx/kubernetes-ingress/blob/v4.0.1/examples/custom-resources/oidc/nginx-ingress-headless.yaml) deployed for OIDC.
+{{< /note >}} 
+
 ---
 
 ### Snippets and custom templates