Preheat oven to 350 degrees.
Heat the oil in a large, deep skillet with a tight-fitting lid over medium heat; add ham and cook for 2 minutes or until warm and lightly browned.
Add next 8 ingredients (oregano through eggplant) and cook for an additional 5 to 7 minutes or until vegetables are tender-crisp. Add zucchini, tomatoes and tomato sauce.
Bring mixture to a light boil and cook for 5 minutes. Stir in Ricotta cheese then top with shredded Mozzarella.
Cover skillet, remove from heat and allow mixture to set for 5 minutes or until Mozzarella has melted. Serve immediately.