Helping with multiple DNS servers on client

I have a ubuntu VM that I want to use two different DNS servers for 2 different zones. DNS server A used for domain X and DNS server B used for domain Y. Right now, I have this

root@:~# cat /etc/resolv.conf nameserver A nameserver B 

and it's not working. Queries to Y fail at A with a NXDOMAIN and never make it to B. Any suggestions? I can't alter the DNS servers.