If the thermostat is stuck closed, if you take it out it'll just let the coolant travel to the rad from the off. So if that was your problem and it was removed then I guess the car wouldn't then overheat. I'm not expert so best wait for others who know more to reply. Had a stuck thermo on my fiesta and yes she would over heat a lot. Change it out and sorted. I don't know how easy it is to do on the zed though.
Sent from my GT-I9300 using Tapatalk