extract whois info from zone files...

[maroulis]

is there any quick tool that will help me extract whois info from zone files? I have a customer who wants to find out all domains owned by a registrar based on either NS or simply contact on whois info...

any help appreciated...

thanks

PS I tried doing reverse IP but the NS won't return the list of domains which is approx 4000 according to whois.sc NS Spy. Since I can't get access to the list of those 4000 domains to run them via DRT I was hoping there must be another way to do this...