This version of the API shipped with Indigo 6.0.4 - check the API Version Chart to see what version of the API is available in which Indigo versions.
zoneEnableList attribute, which is a list of booleans. Every zone in a sprinkler device is considered enabled (True boolean) unless its maximum zone duration is set to 0, or it is the last zone on the device and the PumpControlOn property is set to True.