1994 Buick Century compression

i have a 1994 buick century with a 2.2L, i was driving at 50mph running good as usual. it quit. i pulled to the side of the road it had fuel and spark so i checked compression, i had 40 psi on cyl 1 and 4. i had zero on 2 and 3. Could it be the timing chain? any suggestions?

thanks
Glenn