Route 53 Subdomains not working.

Going back one step, you've purchased petstore.net through CloudFlare and have delegated administration of it to Route 53. Is this part working okay, i.e. can you create a dummy record like testing.petstore.net in the route 53 public zone and it propagates correctly?

If this doesn't happen then delegation isn't working properly, so something in here has been missed https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/migrate-dns-domain-in-use.html

If delegation is working then the next step will be creating a Route 53 public zone called xyz.petstore.net, noting the name servers this is populated with, and then adding these as NS records for the record name xyz.petstore.net in the Route 53 public zone for petstore.net

Full steps for this are here https://repost.aws/knowledge-center/create-subdomain-route-53

And the accompanying video illustrates the steps https://www.youtube.com/watch?v=YHBnLJiKv0M

Did you create the subdomain zone as a Private or Public one? If the "xyz.petstore.net" NS record in the "petstore.net" hosted zone is pointing to the right aws ns servers (of the subdomain hosted zones) AND CloudFlare was properly set with the NS records pointing to "petstore.net" zone ns servers....it should work.

Did you get this working eventually? I do have the same problem with another .net domain I purchased through amazon route53. I did everything according to the documentation given by aws for subdomain delegation. NSlookup for the domain is working, but its not finding anything for the subdomain.

Created hosted zone for the subdomain and created a record in the domains hosted zone with the details of the subdomains records.