No one?

So, I went ahead and created another zone for the domain sub.example.com, set the A records and a host (test1.sub.example.com) and everything seems to be working. Then I tried going to my parent zone and created an A record for host (test1.sub) to see if it would override or something (it shouldn't), and it didn't. I assume this is all because I didn't delegate to different name servers?
Anyway, I think this is working and I didn't have to mess around with any NS records. If I did something wrong, someone please tell me. Otherwise, I guess I'm good to go.