Has any digging occurred recently?
Do you have a multimeter? If so, I would suggest:
- Turn on a zone and check the power output at the terminals for that zone (should be 24 VAC)
- If you have power, turn off the zone and check the wiring, especially the common wire(s) at the controller
- Check the impedance of one of the valves from the controller. For more information on this, see a forum post such as: Runaway zone
It seems rather unlikely that ALL of the valves went out. That is why I am suspecting common wire(s) and/or the controller itself.