You are overthinking the wiring. First, you wire the two loops to two of the controllers on the ZW. That way you can run conventional (using the handles) on each loop if you want. Second, the ZW-L responds to TMCC/Legacy commands so you can use your controller to operate the loops. And, third, since the grounds on the ZW are interconnected, you can operate TMCC/Legacy engines on either or both loops when you set their respective ZW controllers to a full 18 volts.
If you have any crossovers between the loops, you'll need to inset an insulating pin in the center rail of the crossover.
Jan
