Preheat the oven to 400°F. Place the shredded zucchini in a colander, and sprinkle with salt. Let stand 10 minutes, then squeeze out the moisture.
Combine the zucchini with the eggs, Parmesan, and half the mozzarella and cheddar cheeses. Press into a greased 13x9-inch or 3-quart baking dish. Bake for 20 minutes.
Meanwhile, in a large saucepan, cook the beef and onion over medium heat until the meat is no longer pink, breaking it into crumbles. Drain. Stir in the tomato sauce. Spoon the meat sauce over the zucchini mixture.
Sprinkle with the remaining cheeses. Top with green pepper. Bake until heated through, about 20 minutes longer.
