Settings->Zones->[Click one zone]

At the bottom of each Zone settings should be an "Enable" toggle.  Toggle it, so it is not enabled.  Save.

Repeat for all of the zones you wish to disable.

OR

If you want to disable all zones: Just unplug your Sprite.  It cannot trigger watering if it is unplugged.

Neither of these approaches should cause you to lose your default schedules.