The shot actually passed through both men at z222/223.
I wonder what someone like Benjamin Cole has to say about all this?
To me, jiggle analysis of the Z-film is the best way to determine when the single bullet struck. All of the calculations below are based on approximations because that is sufficient for this exercise.
We can start with the headshot because that is the most obvious to pinpoint. The distance from the sniper's nest to JFK's head was 88 yards(264 feet). At an average velocity of 2000 fps, it would have taken 0.132 seconds for the bullet to reach JFK's head. Each frame of the Z-film covers 0.0564 seconds. That works out to approximately 2.34 frames of the Zapruder film meaning the bullet would have been fired in the Z310-311 window. There was an obvious camera jiggle and Z318, meaning there was a lag time of 7-8 frames from the time the bullet was fired to the time Zapruder reacted to the muzzle blast.
Since the distance from the rifle to Zapruder's ears was a constant for all three shots, we should expect a similar lag time for all 3 shots. There is an obvious jiggle at Z227. Applying the same 7-8 frame lag time between the shot and the reaction, that would indicate Oswald fired the single bullet in the Z219-220 time frame. The distance from the rifle to JFK at that time was roughly 190 feet. Using the same estimated average velocity of 2000 fps, it would have taken .095 seconds for the bullet to reach JFK's back. That is 1.68 frames so a bullet fired at Z219-220 would likely have struck in he Z221-222 time frame. That would have been 2-3 frames before JBC's jacket bulged out and 4-5 frames before both JFK and JBC flipped their arms upwards. This all seems very reassonable to me.