Based on your description, I have good news and bad news.
Bad news: Sounds like the timing belt broke. You can verify this by removing the shroud over the cam gears on the passenger side of the engine. If the belt is obviously missing or does not appear to be firmly in place over the cam gears, there's your problem.
The good news: Ford made the Zetec a "non-interferance" engine. That means that if the timing belt should brake, the pistons will typically not impact the valves and severe engine damage is usually avoided.
There are rare instances where the engine is damaged, but this is most typical in very worn engines, or if the car is being driven hard (high RPM) at the time the belt breaks.
Your local shop or dealer should be able to replace the belt & reset the valve timing without much difficulty. I estimate the cost to be under $600.
