Simple DNS Plus "super master" and "super slave" servers synchronize their zone lists using an automatically updated "_zonelist" zone - containing one record for each zone.
It is possible to "fake" a super master with a 3rd party DNS server by creating a "_zonelist" zone, and adding a PTR-record for each zone that you wish to sync in this. The name of each PTR-record should be "_zonelist", and each PTR-record must point to a unique zone name.
Obviously you will need to keep the "_zonelist" zone updated manually (Simple DNS Plus super masters do this automatically when you add/delete zones).
Note that this is a bit different from the records in a "_zonelist" zone automatically generated by a Simple DNS Plus super master. Those records also contain the current SOA serial number and suspension status for each zone (special NULL record which cannot be faked in a normal DNS zone).
So "faking" a super master is not as efficient - but it works.
It is not really possible to "fake" a super slave, as 3rd party DNS servers would not know what to do with the "_zonelist" zone.