I'm sure you can, but why not go with a turbo?

"HMS Inc is proud to announce that it has,working with a supplier,developed two kits for the Zetec. Stage One is 190-200 BHP @ around $2600.Stage Two is 280-300 BHP @ around $3800. It should be noted that both these packages will fit Zetec in Contour and Focus,some engine teardown is required."

See thread.
http://www.contour.org/cgi-ubb/ultimatebb.cgi?ubb=get_topic&f=50&t=000004

Ryan French

98 Mystique Duratec Sport(KKM, Custom Exhaust, debadged/dedinged, Tinted, A4 sidemarkers(clear), Bodycolor grill...Suspension is next.)

00 ZX3 Zetec Limited Edition(nothing)