What other exercise build strength on my forehand and backhand?

The exercise I like is with the medicine ball. the two players stand back to back and they pass the medicine ball around so to rotate to my right and pass the ball to my partner who’s behind me and he rotates all the way around giving the ball to me on his right and I do the same and we continue in the rotation after 10 rotations. Then we go the other direction which builds tremendous core strength and trunk strength. This will help your forehand and backhand.