To Prepare the Zucchini: Preheat the oven to 425 degrees. Slice the zucchini lengthwise about ¼ inch thick. Arrange slices on 2 baking sheets sprayed with cooking spray. Bake about 15 minutes, or until zucchini is just starting to brown around the edges.
To Prepare the Meat Layer: (This is an optional step if you're making the meat version. If not, skip the meat, but still do the sauce and seasonings.) Spray a large sauté pan with cooking spray. Heat pan over medium heat, and sauté garlic for a few seconds. Add the ground meat and cook, stirring occasionally until browned through. Add sauce in the last couple minutes of cooking and stir until meat is cooked and sauce is slightly thickened. Remove pan from heat and stir in seasonings.
Layer: Spray a 9x13-inch baking dish with cooking spray. Arrange a single layer of non-overlapping zucchini slices, cutting them if needed to cover the bottom of the dish. Spread with one-fourth of the sauce, then sprinkle with 1 tbs Parmesan. Repeat for three more layers (or until you run out of ingredients).
Topping: Finish by spreading tomato sauce and mozzarella and parmesan cheese evenly over the top. Bake about 20-25 minutes, or until cheese is bubbly and lightly golden brown. Remove from oven and let cool for at least 15 minutes before slicing. Enjoy!