2002 Ford Explorer Engine died and will not start No compression one side What is most likely problem?

I'm not a mechanic, but if this is a 4.0 L SOHC V6 engine, they have 3 timing chains. A main timing chain from the crankshaft to a "jackshaft" which is located where the camshaft is on the 4.0 L OHV engine. A 2nd timing chain from the jackshaft to the driver's side cylinder head at the front of the engine, and a 3rd timing chain from the jackshaft to the passenger side cylinder head at the back of the engine. When you said you have no compression on one side, I wonder if something has happened to one of your secondary timing chains ?