Combine the zucchini, eggs, onion, flour, Parmesan cheese, mozzarella cheese, and salt to taste. Stir to combine ingredients. Heat a portion of oil in a skillet over medium-high heat. Cook as you would pancakes. (Drop heaped tablespoons of mixture onto skillet and cook a few minutes each until golden. Great served with Salsa and Sour Cream for dipping!