it's easy actually
i have asked the same question before and gate2vn answered me
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Ok i have a domain mydomain.com
and i have like 2 reseller accounts A and B
i have IP1 and IP2 from reseller A
and IP3 and IP4 from reseller B
in my domain registrar i made the following
added a new host
ns1.mydomain.com -> IP1
ns2.mydomain.com ->IP2

DNS1.mydomain.com -> IP3
DNS2.mydomain.com -> IP4

now for my clients at reseeler A i give them ns1.mydomain.com,ns2.mydomain.com

now for my clients at reseeler B i give them dns1.mydomain.com,dns2.mydomain.com

and that's it

BTW : my reseller A is linux and reseller B is window
and sorry for the late reply
and thanks for gate2vn