The arm and scapula (shoulder blade) are attached together by the rotator cuff as an assembly. That assembly is attached to the body by many muscles that attach to the scapula. To do balancing exercises the motions and muscles should be identified and strengthened by balanced exercises, equal weights and reps. Some exercises emphasize flexibility and endurance and may involve only small weights/forces.
Since many people might not know how to strengthen, for example, the Rhomboids or Serratus Anterior, it takes some research. The posture of the most sport active scapula should be compared to the other scapula. That takes expertise. Search - scapula posture
Shoulder injuries to baseball pitchers are often attributed to scapular posture and imbalances. Corrections involve specialized exercises such as the Blackburn exercises to align, strengthen and build endurance for the scapular muscles such as the Rhomboids. The Rhomboids are interior to the mid trapizeus and don't show that much.
Just exercising without a posture evaluation and understanding the muscle functions may cause problems.
Probably the Throwers Ten is a good general program and a book such as Complete Conditioning fro Tennis
, Roetert, Ellenbecker, would provide some generally good information on exercises and stretches. Keep in mind that you may have a serious imbalance that a well qualified Dr or physical therapist might be able to see.
Discussion of a few common imbalances not necessarily specific to tennis.
This Todd Ellenbecker video discusses shoulder anatomy and at minute 8 has important advice on shoulder orientation for the serve.