That is currently not possible for Dynatrace Managed, but it is for Dynatrace SaaS. The difference here is that Network zones in Managed apply to many environments and it's not possible to create a link to proper environment to display deployment status of OneAgents.
This will be enabled once we bring the visibility of all deployed OneAgents to all environments in CMC. Same as we did recently with ActiveGates. I have not ETA for that yet.
Thanks @Radoslaw S. for confirming this.
So for now I need to find out what are those 6 oneagents out of a long list that are reporting to default N/W zone , but ideally should report to a custom defined one and then fix those.
Checking logs of DT Managed Cluster should be the only option I guess(just let me know in case there is any other way)