Some DNS server implementations have a feature where you can have different versions of a zone served to different clients based on which IP address the DNS request originates from. This is often referred to split-horizon, split-view, or BIND views.
Very often this feature is used to handle the situation where clients on a private LAN need to access a server using a private IP address and clients from the Internet need to access the same server using a public IP address.
Simple DNS Plus does not have the ability to serve different versions of the same zone, but it does have a feature that makes it easy to serve private/public IP addresses as in the case above. This called the "NAT IP Alias" feature, and is found in the Options dialog / DNS / NAT IP Alias section:
With the configuration show above - any request from 192.168.0.xxx for a host record that points to 184.108.40.206 - will be served a "cloned" host record pointing to 192.168.0.4.
So rather than maintaining duplicates of one or more zones, you can simply configure this in one place.