If you have IPv6 transport to your nameservers, said nameservers would ideally be listening on an IPv6 address configured into the nameserver and be dual-stack, responding to queries via both IPv4 and IPv6 transport.
Getting the IPv6 transit is the hard part, but much easier than it used to be. While outside the scope of this chapter, you would discuss this with your upstream connectivity provider. Once that's in place, it's a simple configuration update to get most nameservers responsive over IPv6:
listen-on-v6 { 2001:678:5::13; };
#################################
# local-ipv6 Local IP address to which we bind
#
local-ipv6=2001:678:5::13
do-ipv6: yes