Preheat an oven to 200 degrees C. Place the zucchini in a colander and sprinkle with salt; let drain for 15 minutes then squeeze out the moisture.
Combine the zucchini, eggs, parmesan, 1 cup mozzarella and 1/2 cup cheddar in a large bowl. Press the mixture into a greased 20x30cm baking dish. Bake, uncovered, in the preheated oven for 20 minutes.
While the zucchini base is cooking, heat a large frypan over medium-high heat and stir in the beef mince and onion. Cook and stir until the beef is evenly browned, and no longer pink. Drain and discard any excess fat. Stir in the tomatoes and Italian seasoning.
Spoon the sauce mixture over the baked zucchini base. Top with the capsicum, mushrooms, black olives and the remaining mozzarella and Monterey Jack cheeses. Return to the preheated oven and bake for 20 minutes or until heated through. Let sit for 5 minutes before serving.