Place the zucchini, flour, baking soda, Parmesan cheese, garlic powder, oregano, marjoram, basil, black pepper, and kosher salt into a large bowl, and stir to thoroughly mix. In a separate bowl, beat the eggs with buttermilk, and stir the egg mixture into the zucchini mixture to make a batter.
Heat the vegetable oil and olive oil in a large skillet over medium heat until the oil shimmers with heat, and gently spoon about 1/4 cup of zucchini batter per fritter into the hot oil. Fry the fritters in batches until golden brown on both sides, about 3 minutes per side; drain on paper towels, and set the fritters aside to keep warm.
To serve, place a slice of mozzarella cheese and a slice of tomato on top of each fritter; sprinkle with sea salt.