$ORIGIN tld.

ns.bar.tld 3600 IN A 127.0.0.1
ns.bar.tld 3600 IN AAAA 0:0:0:0:0:0:0:1

ns-only.tld 180 IN NS ns.foo.tld.
ns-only.tld 180 IN NS ns.bar.tld.

ns-and-ds.tld 180 IN NS ns.foo.tld.
ns-and-ds.tld 180 IN NS ns.bar.tld.
ns-and-ds.tld 86400 IN DS 1 2 3 000102

ns.foo.tld 3600 IN A 127.0.0.1
ns.foo.tld 3600 IN AAAA 0:0:0:0:0:0:0:1