If your using 2 different transformers. Even if one is used to only power the DZ switch machine. If the relay is using the same power and also powering the rails around the diamond. I would think they would have to be in phase. Even if it’s just a couple of small rails. It will still act like a power district.
I think Ken’s got the right idea. Power the DZ stuff with the same transformer as the rest of the track and see what happens.
I’m a Tortoise guy. 12vdc to the switch motors. I then use the accessory terminal switches to power 12vdc automotive relays. The contacts on the relays use track power. So no chance of a phasing problem.