Hi Mark and welcome
I owned a 2003 Mk6 1.4 Duratec (which is the Zetec engine rebadged )(then to confuse things, Ford started branding their cars as Zetec too lol), did over 36K in it in 3 years
Never really impressed by the fuel economy on that engine, although other might disagree with me.
Nothing major went wrong - it had a new driver's electric window winder regulator and a new rear window when one of the elements in the heated screen packed in - both common faults i believe.
Oh and it had a change of head unit when it tried to swallow one of my CDs, also a common fault on early models i think
I get 43 MPG and do about 75~80 on the motorway...