I currently have 2001:1973:2303::/48 assigned to me and i'll be assigning /64's to customer's

I'd like to have 1 zonefile for the /48 where i can essentially point / redirect query to different nameservers.

Example ( Desired effect )

2001:1973:2303:1234::/64 -> ns1.example.com, ns2.example.com
2001:1973:2303:2345::/64 -> ns99.example2.com, ns100.example2.com
2001:1973:2303:4321::/64 -> ns1.cust1.com, ns2.cust1.com

Current /48 zonefile

$TTL 3h
$ORIGIN 3.0.3.2.3.7.9.1.1.0.0.2.ip6.arpa.
@ IN SOA ns3.example.ca. ns4.example.ca. (
    2011071030 ; serial
    3h         ; refresh after 3 hours
    1h         ; retry after 1 hour
    1w         ; expire after 1 week
    1h )       ; negative caching TTL of 1 hour
        IN NS   ns3.example.ca.
        IN NS   ns4.example.ca.

1234 IN NS ns1.example.com.
    NS ns2.example.com.
2345 IN NS ns99.example2.com.
    NS ns100.example2.com.
4321 IN NS ns1.cust1.com.
    NS ns2.cust1.com.

Where am i going wrong ? My request seems simple to me atleast. To put it in terms of firewalling i want to redirect traffic

client queries 2001:1973:2303:4321::1 -> ns3.example.ca sees the request and redirects the query to ns1.cust1.com -> ns1.cust1.com answers the query with omg.itworks.ca ( provided ns1.cust1.com is properly configured.