Thanks for posting in Q&A platform.
Based on provided information, I did some test in my lab, and attaching the test result for your reference.
Windows server with AD DS and DNS role:
Another Windows server with DNS role:
Make sure that there is a Host Record of newdhcp in DC1
Configure New Delegation on DC1
Insert FQDN of the DNS server which you want it host the subdomain:
On another DNS server (newdhcp), under forward lookup zone create a new primary zone with zone name: sub.sunny.com. And then add a host record in this zone for testing.
Test from DC1, delegated zone can be resolved successfully
Test from another windows machine, delegated zone can also be resolved successfully:
If the Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.