Start by shredding your zucchini until you have about 4 cups. Sprinkle with salt and let sit for about 10 minutes.
Squeeze out as much moisture as possible from the zucchini using a clean kitchen towel or cheesecloth.
In the same bowl, add eggs, grated Parmesan cheese, and half of the shredded mozzarella cheese. Mix until well combined.
Grease a 9x13-inch baking dish and press the zucchini mixture into the bottom to form a crust. Bake at 400°F for about 20 minutes.
In a skillet, cook ground beef and chopped onion over medium heat until beef is no longer pink. Drain excess fat.
Stir in pizza sauce, chopped bell pepper, sliced mushrooms, oregano, garlic powder, and black pepper. Cook for another 5 minutes.
Spread the beef mixture over the zucchini crust. Top with remaining mozzarella cheese and all of the cheddar cheese. Bake for another 20 minutes.