How to I tell le master account to push requests for .testing.example.com down to le child account.
The requests are referred, pas pushed, mais you can achieve le desired outcome by delegating le subdomain to a différent set of Route 53 servers depuis those that host le parent zone.
Look at le nouveau hosted zone you created for testing.example.com. Cela peut be in le même AWS account, a différent AWS account... tout AWS account. Il y a nothing here that is "account" related. This uses standard DNS configuration. The whole of DNS is a hierarchy. The global root can tell you où to find com, et le com servers can tell you où to find example.com, et c'est nothing materially différent for example.com to tell you où to find testing.example.com à la place of giving you a direct answer.
Note le 4 name servers that Route 53 assigned to le testing.example.com hosted zone. Verify that they are tous différent than le ones assigned to le example.com hosted zone. (For tout of them to be le même should be impossible, mais verify this.)
Now, back in le example.com zone, créez un nouveau resource record, avec hostname testing, using record type NS, et enter le 4 name servers that Route 53 assigned to testing.example.com, in le box below.
Now, quand a request for testing.example.com et anything ci-dessous it arrives at one of le Route 53 servers handling example.com, le reply will not be le answer depuis testing.example.com -- le reply will provide le requester avec le 4 NS records associated avec testing.example.com et an answer equivalent to "Je ne know, mais try asking one of these guys."
C'est how c'est done.
