At my shop where I work all day, we NEVER let cars go past 90k miles. And if the OEM manual sais less, then we recommend less. Especially since so many engines these days are 'interference' engines, meaning that valve to piston collision and damage MAY occur. The reason I say MAY is because with interference engines, damage doesn't always occur. Sometimes if the motor was just idling when the belt failed, then it may not ALWAYS cause damage. But if it failed at cruising engine speeds, interference motor will always bend valves. I'd check with an OEM Ford manual to find out if the Zetec is for sure NOT an interference motor, because just that simple lack of knowledge is a difference of several hundred dollars in repair costs. I DO have an OEM Ford CD Rom at work that would tell but I'm not there so I can't give you the data right now. But for something like a timing belt, I would just put a new one on for how many miles you've got.
