I can get around that issue and setup your DNS no problem whatsoever and helping people with DNS setup is something that I also typically don't charge anyone to do, often I just help people with that as a favor to anyone who typically asks me for my help since it usually only takes a few very quick moments to get DNS setup properly.
I actually have to leave right now and drive across town so I don't have much time to write a lengthy instruction message for everyone on how to properly setup DNS on Cpanel or getting around the "invalid domain" issue on the current release but if I get a few free moments, I can try to come back and do that so that everyone can know the ins and outs of what needs to be done to setup the DNS nameservers in more in depth detail.
The super quick basic overview though ---
On the issue of Cpanel rejecting the domain, you mainly need to add the domain to the server first per item #3 above and add an "A" record to the zone for the primary IP to be used for that domain itself. If that domain won't be having it's own website, just simply give it an "A" record with the primary IP address of your server.
1. You need the DNS hostnames and IP registered under your domain at your registrar where you
originally purchased your domain name.
2. You need the same DNS hostnames and IPs listed in /etc/nameserverips
3. You need the DNS zone for your primary DNS domain added to your server either as a Cpanel account
(if you will have a website on your primary domain) or as a DNS zone file alone (if no website) and in
the zone file for your primary DNS domain, you need both NS and A records setup with the DNS hostnames
and related IP information for your new DNS servers.
4. In the "Basic Settings" section of WHM and/or reseller config whichever is applicable, you also need to setup
the same DNS hostnames so that any new domains added to the server will automatically build DNS zone files
which already by default point to the correct DNS hostnames.
That's really basically all there is to it. I don't really have time at the moment to go into a more lengthy discussion on DNS setup but the above is the main basic essentials of what you need to do.
EDIT: PS: Do NOT put your DNS hostname(s) and/or IPs in "DNS resolvers" or directly in the '/etc/resolv.conf' file! A very common mistake people often make is putting their own DNS hostnames in that section. Actually the DNS resolvers have nothing to do with the DNS resolution of any of the domains on your server. It's instead used to resolve domains elsewhere not located on your server such as being able to connect to Cpanel to download updates and so forth. You would not normally use your own hostnames or server IPs as the DNS resolvers.