For DNS / Cpanel & multisite experts. Mail one one server, web on another

I !

I have a tough one....

Here is the scenario :

the client wants to keep mail management on HIS serveur
but the website is on MINE.

Problem : on cpanel, domains must be parked on top of main site domain in order to be mapped on the multisite.

This is very complicated...

SO : the domain must have a A entry pointing on MY server. Its ok.

BUT what settings must I do on MY server for the DNS zone ?
Since :
- the DNS is not mine but the client one
- only need the web service

So : should I duplicate the whole DNS settings
Or just a simple DNS zone with the NS and A entries ? (and of course the www cname) and remove all other settings specially MX entries ?

Thanks for tips i am quite... lost