This main dish casserole is a delicious combination of cooked diced chicken and zucchini. Serve this chicken, zucchini, and dressing casserole with your favorite side salad or sliced fresh tomatoes. Stuffing crumbs and shredded cheese make up the topping for this savory chicken casserole. Use leftover chicken or turkey in the recipe or use a rotisserie chicken or packaged fully cooked chicken breasts.