Heat oil in skillet on medium heat. Add onions and cook 2-3 minutes until softened but not brown.

Add ground beef. Break up the meat and cook, stirring regularly, until fully brown, about 4-5 minutes. (Drain any excess fat at this point, if applicable)

Add Italian seasoning, salt and pepper and minced garlic. Stir and cook for one minute.

Add diced tomatoes, tomato sauce and water. Mix well to make a sauce. Bring to a boil, then lower the heat and simmer, uncovered, for 7-10 minutes.

Add Parmesan cheese and zucchini and stir until well coated in sauce. Remove from heat.

Transfer mixture to a 2- to 3- quart casserole dish. Top with shredded Italian cheese.

Cover and bake in a 375F oven for 30 minutes. Remove cover and bake an additional 10 to 15 minutes uncovered. Remove from oven and allow to rest at least 10 minutes before serving.