DNS hosting issues

hello,

I have encountered today a problem, and I am not sure how exactly to fix it. I mainly seel web hosting to end users with my reseller plans or VPSes, and so far I didn't have to host DNS.

Today, I have received a request for DNS hosting from a new client.
He has his servers hosting his domain somewhere, and he want's to host his DNSes elsewhere.

I am an enom client, so I will use their services for this.

So, I will host his DNS with enom, with their nameservers.
What configs do I have to do, and what configs does he has to do?