I have a Furuno DRS4D Radar working with my MaxSea Timezero Explorer v2.0.3 software, with my TZT14 switched off.
The radar is powered with a PSU017.
The Ethernet cables between the DRS4D, PC, FA50 (AIS) and TZT14 (switched off) are connected via a Netgear switch (GS108). It is important that an independent switch is used (a hub would probably work as well), rather than using the Ethernet connections at the back of the TZT14, as switching the TZT14 off would stop the network from working if the TZT14 connections were used.
In MaxSea, I selected Menu->Options->Initial Setup->Advanced Settings->Radar Connection->"NavNet TZtouch" or "FAR 21x7". Do not select "Automatic" for the Radar Connection option as the radar does not show up in Maxsea if the TZT14 is not switched on. The "Advanced Settings" option is at the very bottom of the "Initial Settings" page.
With the above configuration ("NavNet TZtouch" selected), I am able to run the radar in Maxsea independently of the TZT14 - it does not matter if the TZT14 is switched on or not or even if the Ethernet cable from the TZT14 is disconnected.
With the TZT switched on and its ethernet cable connected, I can run the radar from either the TZT14 or Maxsea.
I have not done any modifications to the system. The software on the DRS4D was upgraded to version 16:03:03:02 (version per the TZT14 'Sensor List" menu), when the technician in the USA installed the TZT14 and PSU017 (both supplied by Furuno USA).
I suspect that I would have been able to run the DRS4D from Maxsea even if I had never had a MFD, provided the software version on the DRS4D was correct.