They're all 8v mate. it's only the new 2.0 and the 1.4/1.6 i think? thats 16v

Also Zetec is just a trim level aswell, iirc it's CL, Zetec, LX & Ghia
There is also a Zetec engine as we know, but just because it says Zetec on the back don't mean it's a petrol.

They're ok really, both tddi and tdci suffer pump problems so it's not worth buying one over the other because of the risk of it going wrong, infact a tdci pump is alot cheaper than a tddi pump.

timing belt is due at 100k miles though so watch for that.

Also all models have a timing belt, yes it's the same engine from the escort with minor tweaks, the focus diesel uses a chain from the crank to drive the pump then a belt from the pump to the cam.

The tddi is almost the same as the escort diesel engine with a couple of tweaks which include a Bosch VP30 fuel pump [try google]

The tdci is again the same engine expect it runs common rail and ecu controlled injectors.