How to access a private zone via DNS peering

I understand that your goal is to reach an instance in VPC-A from VPC-B by its internal (to VPC-A) DNS name by dns-peering VPC-B to VPC-A.

If my understanding is correct, it is not only possible, it's the idea of dns peering. I just created a lab, where I:

• Created VPC-A in Project A
• Created VPC-B in Project B
• Created an internal DNS zone (vpc-a.internal) in VPC-A with one A record pointing to the instance in the same VPC (ip=172.16.1.209, name=instance-1)
• Created a peering DNS zone in VPC-B and pointed it to VPC-A (peering in unidirectional relationship, no need to do the same in VPC-A)
• Created an instance in VPC-B (test-instance) and dig'ed that previously created A record:

username@test-instance:~$ dig +short instance-1.vpc-a.internal
172.16.1.209

As you can see the resolution works. Please note, that DNS Peering is about being able to resolve names, and not about being able to access. If you need to access instance-1 in VPC-A from VPC-B then you need to establish VPC peering as well.