Well for one, the Zetec blocks are iron, the Duratec blocks are Aluminum.
I own both, the 03 zx3 Duratec 2.3L PZEV manual, and 2.0L Zetec DOHC Auto in my 00 wagon.
The 2.3l is much funner. And in my mind, more reliable.
Not to say the Zetec isn't reliable either, but I do feel more things go wrong on it.
2000 SE wagon 2.0l Zetec.