Preheat your oven to 400°F (200°C).

In a mixing bowl, combine the shredded zucchini with salt and let it sit for 10 minutes.

Squeeze the zucchini mixture to remove excess moisture.

Combine the drained zucchini, eggs, Parmesan cheese, and half of the mozzarella cheese in a large bowl.

Press the zucchini mixture evenly into a greased 9x13-inch baking dish.

Bake the crust in the preheated oven for 20 minutes.

In a skillet, cook the ground beef and chopped onion until browned, then drain excess fat.

Stir in the pizza sauce, bell pepper, mushrooms, oregano, garlic powder, and black pepper and cook for 5 minutes.

Spread the beef mixture evenly over the baked crust.

Sprinkle the remaining mozzarella cheese and cheddar cheese on top.

Return to the oven and bake for an additional 20 minutes, until the cheese is melted and bubbly.

Allow the casserole to cool for a few minutes before slicing and serving.