How to use a sprinkler valve in multiple zones?
You can't get there from here... diodes can't steer the AC suffciiently on both halves of the AC cycle.

If you put diodes in for the other half-cycle there's a back path that powers the zones that should be off.

consider zones 5 and 6







simulate this circuit &ndash; Schematic created using CircuitLab

I'm sure you've figured out that this will not work:
when zone 5 is on current can flow through D1 and D4 during the positive half and through D2 and D3 during the negative half. in each case reaching zone6 which is not wanted.

If the manifold solenoid will work from DC you can do this







simulate this circuit

If it does not you will need to use a relay designed for AC operation.







simulate this circuit

Or maybe use triacs to gate the power to the manifold solenoid.







simulate this circuit