You can use same nameservers (for instance ns1.d.com & ns2.d.com) for as many domains as you want.
You just have to add the two name servers as NS records in the DNS zone for each website, both of them pointing to that website domain. And add both name server as well, as A records also for each domain you use them with.
Create your other reseller accounts by using sub domains(for example: reseller2.yourdomain.com). Also you must add CNAME for this sub domain and must add A record for ns3.yourdomain.com and ns4.yourdomain.com on your main reseller account(you can do it under "Add a DNS Zone" menu on WHM if you are using Cpanel). This is the best way.
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