DNS Configure Two (2) or more domains in the same server

Hi, this could be very frustrating for the rest of us. I am running OS X 10.3.8 Server with one domain and everything works fine. We only have one ip address. I need to configure a second domain with the same ip address, and probably, sometime later a third domain, with the same ip address too. Right now there is a zone with its records and a reverse file configured for this domain. How a second domain has to be configured? I look for this and did not find any help how exactly this second domain has to be configured. Any help, address, mail is very welcome. Thanks