DNS Slave Server Setup

In trying to setup DNS per the instructions on here :
I get all the way down to the section “Setting the Master IP Address” but there are issues with the documentation. Specifically where it says “In the Zone file options section, find the Default master server IP for remote slave zones field.” There is no section “Default master server IP for remote slave zones”, so where is it supposed to be input? I have played with putting in the IP in different places and no matter what I get this error “Failed to create virtual server : Invalid master IP address : none” I attached a screen shot to show it’s not there.

On the same note, before using Virtualmin I had a dedicated NS1 and NS2 under which I had all my hosted domains set up as such:

lassobin.com. IN NS ns1.hldns.com.
lassobin.com. IN NS ns2.hldns.com.
ns2 IN A
ns1 IN A

Is there a way to setup Virtualmin so it can be for hosting and mail only where the DNS can simply be managed on the other 2 servers rather than the hosting box?

i think you need to disable DNS service on virtualmin if you have another ns server for domains hosted on virtualmin.
I have the same situation, 10 domain with email hosted on virtualmin server but I use another dns server .