Preheat the oven to 425 degrees F (220 degrees C).
Grate the zucchini using a cheese grater. I recommend using the smallest-sized holes on a box grater to get the mixture as uniform as possible. You should end up with 2 cups of packed grated zucchini. Use your hands or a towel to squeeze out as much moisture from the zucchini as possible. You may also place the zucchini over a sieve and use the back of a spoon to press down on it to remove the moisture. Once you remove the moisture, you should end up with about 1 1/4 cups of packed, squeezed zucchini. Add this rung-out zucchini to a medium-sized bowl.
Add 1/2 cup of mozzarella, parmesan cheese, breadcrumbs, egg, garlic powder, onion powder, and salt (if using) to the bowl with the zucchini. Mix until well combined ). It may seem a little dry at first, but keep mixing to allow the moisture from the egg to incorporate the ingredients together.
Line a 9 by 13-inch baking sheet with parchment paper and pour the zucchini mixture into the baking pan. Use a spatula to smooth it out into a flat, even layer about 1/4 inch thick, pressing down well to ensure that the top is smooth
Bake this layer for 18 to 20 minutes or until dry to the touch, then sprinkle the remaining 3/4 cup of mozzarella evenly on top. Top with any additional toppings of choice.
Place the pan back into the oven for an additional 5 minutes, or until the cheese fully melts. For golden brown cheese, set the oven to broil and broil for 1 additional minute (keeping a very close eye to ensure it doesn't burn) (Image 8). Let it cool and slice it into pieces to serve.