DuraTORQ is the diesel one Zetec was the engine used from 1992 on The Zetec Sigma (Zetec SE) was then introduced which was co-developed by Yamaha and used in the Puma (+ others) Then the Duratec engine (when being developed called the RoFlow Zetec) superceded the Zetec.
So, no, the Duratec isn't just the Zetec rebadged, its like the next generation.
What the actual differences are in terms of mechanics / clever stuff, I haven't got a clue!