Here are some common tricks and some tips for common problems. In the DNS tree, a domain is everything under a particular point in the tree. Domains relate to the naming structure itself, not the way things are distributed. A zone is a pruned domain. Pruning occurs when zones are delegated.
Zones relate to the way the database is partitioned and distributed.
A label is one component of a domain name. Run nslookup and see what nameserver it tries to connect you to. If there is no resolv.conf file, the the resolver uses the nameserver on the local machine. Change the serial number in the SOA for any domains that you modified and restart named. Wait an hour and check again.