There are a couple of ways you can do this, both are quite straightforward.
One option would be to install the Windows 2000 DNS server as a secondary
zone to the NT DNS server and all the records will get pulled over
automatically. You could then change the 2000 server to be the primary.
Alternatively, you can copy the zone file over manually. Stop the DNS
service on both servers and copy c:\winnt\system32\dns\zonename.dns from the
NT box and move it to the same location on the 2000 box. Then you can
restart DNS and create a standard primary zone on the 2000 server choosing
the option to use an existing zone file when prompted.
Once the zone is in place, you will need to change the SOA and NS records to
reflect the change. You can also convert the zone to AD integrated if
desired.