cpanel doesn't support clustering out of the box (except DNS); there's no simply way to do it, but it can be done. What type of setup / budget are you working with? Are you dealing solely with static or database content as well. With more information, we can provide a better solution.
The clustering setup in WHM is pretty straight forward. Set it up and you will have the 2 machines running DNS and the records will be shared with both.
dns zones remain on own hosted server instead of synchronized to all clustered boxes
Without the zones existing on both servers, you would have no failover. The idea is that machine #1 would have ns1 and ns2.yourdns.com and machine #2 would have ns3 and ns4.yourdns.com. When machine #1 is down, machine #2 would continue to answer to DNS requests.