I've just realised it's a diesel. (I just read the zetec bit and thought it was a petrol)
Zetec is the trim level (fords attempt to confuse everybody by using an engine name as a trim level)
The actual engine will the the 2.0 duratorq engine as used in front wheel drive transits. And I've heard reports of these throwing con-rods for no apparent reason.
It may be worth while checking the warranty, as I know the transit engines were covered by a 100k/5year warranty. I don't know if ford also offered it with the cars or not. If the warranty is up, ford will quite bluntly tell you where to go (unless you want to pay them to sort it)