I have had lots of problems disabling zones from both the my yard (by zone) section and now I noticed that disabling the schedule does not work either.
By zone, I could disable one but if I tried to disable another zone it would not accept it. I think the second disable does not work because it is part of a schedule including the first zone that I disabled.
I also noticed today that the Edit Schedule enable/disable button does not work.
During the winter I usually disable everything because plants need to go dormant regardless of how much rain.