No problem! Just passing it forward- follow the advice/guidlines on how to keep the signal strong and, as with anything else, the more you utilize the system the more you understand it. once you get it down DCS is great. And, if you haven't already, definitely get Barry\s DCS Companion, 3rd edition- extremely useful
When you say "power terminal block one from TIU fixed output one and Z4000 Track one// terminal block two from TIU fixed output two and Z4000 Track two." does the bolded portion refer to the Z4000 transformer's own remote control track control system? If it is, while I am unfamiliar with how using the Z4000 track control feature and DCS together works, I do know that they can work together and you can create "Z4K" tracks on the DCS remote. But that's all I know, sorry, man. However, If you are not referring to that feature....
.....and are just referring to the Z4000's two main variable outputs controlled by the handles, then I can help. Happy you're using terminal blocks- helps keep things organized and is great for wiring a DCS layout.
Simple answer to your question: You just need to isolate the center rail you DON"T NEED TO/SHOULDN'T isolate the outer rails.
Explanation: Totally isolating the ground and hot isn't just unnecessary, it can also create problems with the non-derailing features of the switch, possible performance issues when engines crossover, and definitely wouldn't be advisable if you run TMCC/Legacy.
Hope that helps! Keep us posted on how things go!