Preheat the oven to 400°F (200°C).

Toss the shredded zucchini with salt and let it rest for 10 minutes.

Drain the excess moisture from the zucchini using a clean kitchen towel.

Mix drained zucchini with eggs, grated Parmesan cheese, and half of the shredded mozzarella.

Grease a 9x13-inch baking dish and press the zucchini mixture into the bottom.

Pre-bake the crust for 20 minutes or until lightly browned.

Cook the ground beef and chopped onion in a skillet over medium heat until browned.

Add pizza sauce, bell pepper, mushrooms, oregano, garlic powder, and black pepper to the skillet. Simmer for 5 minutes.

Spread beef and vegetable mixture over the baked zucchini crust.

Sprinkle remaining mozzarella and cheddar cheese on top.

Bake for an additional 20 minutes or until cheese is melted and bubbly.

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