Analyze the mechanics of the lat pull down and the chestfly.For lat pull downs and chestflys, identify the prime muscle movers, antagonists...

At least some of the information that you want can be
gathered through an internet search and/or through your own slow, thoughtful reenactment
of the exercises that you name. I've listed two links below for the lat
pulldown.

To get you started, I'll gladly write the
following:

Lat pulldowns primarily work the upper back
muscle group ("lat" = latissimus dorsi) and the biceps. I'm not sure what the opposing
muscle group for the lats are (the deltoids, I suspect; the lat pulldown is pretty much
the opposite of the military press, after all); I'm more sure that the opposing group
for the biceps (in this case, as in pretty much all cases) are the
triceps.

The primary joints involved are the shoulder and
elbow. (The neck could be considered involved, too, especiially if someone has bad form
in the exercise.) I'm not sure what's meant here by "joint involvement" and "Joint
action." I do know that the joints move in a way to close the gap in the exhale phase
(the hard part, the "pull down"): as you pull the bar down, the elbow joint moves to
allow the forearm to come closer to the bicep and the shoulder joint moves to allow the
tricep to come closer to the side of the body. The opposite is true of the inhale phase
(the slightly easier part, the "let up").