Didn’t see anything in the posts specifically about Pi Zero. I just bought my OSPi kit and a Pi Zero W H. The Pi has built-in WiFi and has the GPIO header installed. Ordered from AdaFruit for $14 plus $4.71 shipping. Hooked it up the OSPi board and it seems to work great. Haven’t connected to sprinklers yet but all functions appear usable. Saves a lot of trouble having both wifi and the GPIO header.