DNS server setup in windows 2003 behind firewall

os: windows 2003 R2 SP2
1st dns: primary dns server(setup in local network)
2nd dns: isp provide secondary dns server

widnows 2003 has internal ip address which forward tcp/udp 53 from firewall.

How i setup external ip address and internal ip address in dns zone ?

I don’t have idea how to start.

Thanks