So that you don't do damage to your new TIU, I would add some protection between the TIU and the Z4000. I think the breakers on the Z4000 don't trip as fast as they should.
You can fry electronics on a simple derail. I have simple 10 amp auto blade fuses between the 2, on every TIU channel input. Maybe not the best, but it helps.
There's plenty of posts here about adding protection. GRJ and others can help.