This can be done thru Zerigo. But can't i find the nameservers myself from somewhere and update it at the accound where i purchased my domain from ?
Heroku doesn't provide DNS services therefore there are no name servers.
You use your domain name registrars control panel to point your DNS records at your Heroku application. Typically this is a CNAME record pointing at the .herokuapp.com entry. So www.mydomain.com would be a CNAME to myapp.herokuapp.com.