Oh, the games people play now. Every night and every day now. Never meaning what they say now. Never saying what they mean. And they wile away the hours. In their ivory towers. Till they're covered up with flowers.
ZoneCheck performs several tests on your DNS zone to ensure that it is correctly configured, and can be safely delegated. The Zone name must be either a Domain name, in-addr.arpa zone, or ip6.arpa zone name.
With DNS delegation, it is pretty similar. When the com name servers are asked for the place to find authority of the zone abc.com, they often delegate this work off to separate name servers (in fact in the vast majority of cases, they do in fact delegate the response to other name servers).