After doing a lot of mess in my setups, I´ve realized that it was too simple and now it´s working fine for me. This is what I´ve done :
01. Server / DNS ..... let it as default
02. Client / DNS ...... Just add an A record for the NSs you want to create, for instance, ns1.yourcompany.com and ns2.yourcompany.com
03. Domain / DNS.. let it as default
In your case, you create the client with this A record and all the domains you create under this client will have the same NSs. From what I understand, you´ll have just one domain, but do the record add in the client, because if later, you decide to add another domain, it´ll keep the same NSs of the client.
note: after you create the A record in the client, you see the NSs you´ve created. When you configure the domain, just click on default DNS, you´ll see the same NSs.