Preheat oven to 350. Spray 3-quart casserole with nonstick cooking spray. Chop zucchini.
Combine spaghetti sauce (28 ounce), broth, zucchini, mushrooms and rice in prepared dish.
Bake, covered, for 30 minutes. Remove from oven and stir casserole. Cover and bake 20-40 minutes more or until rice is tender. This may take awhile~keep checking it until the rice is fully cooked and ALL the liquid is absorbed.
Remove from oven, and sprinkle evenly with shredded cheese.
Bake, uncovered, 5 minutes or until cheese is melted.