You shouldn't zero joint at the end, it typically messes up the animations because it resets the joints to 0.
Also, you need to keyframe right after you zero joint (i think, it just makes sense to me that you would..) since it resets the joints, and that would mean you need to keyframe it. Cause if you reset the joints and then moved it, it would be the same as moving an arm, not keyframing, and then moving to a different frame, thus making it not stay...
haha i'm not sure if any of that made sense...