What I learned about Subdomain Setup

You should not have 2 Route53 public zones with intermediary paths that would classify one as a sub-child of the other.

Given the root domain subdomain.dominicklee.net and two AWS accounts that have created the public zones:

^ This will cause an outage if you delegate nameservers from the parent. In this case, Account 2 should have its NS delegated from Account 1 instead of the Root domain.

Another example:

^ In this case, there is no issue, because there is no intermediary zone in the path that breaks the DNS delegation, and both records can be delegated from the Root domain.