May the Force Be with You !

The force that is exerted on a tennis ball starts life as the Ground Reaction force and travels from the legs through to the racket in a chain like wave. Any weakness or break in that chain will result in a weaker and less controllable shot. Thus the path and speed of the racket is dictated by the continuous linking of all the body components from the force generated off the ground by the legs through ultimately to the rotation and uncoiling of the upper body.

The essence of a good stroke is "less is more" (ie the less complicated the motion, the more sound & efficient the result). A simple action will also encourage the more correct use of the important large body parts like the trunk rather than lesser parts like the wrist.

The best advice is KISS (ie Keep It Simple Stupid)