Grate the zucchinis and place the shredded zucchini onto a paper towel-lined plate. Sprinkle with salt and let sit for 10 minutes.
Squeeze the water out of the zucchini using the paper towels.
In a large mixing bowl, beat the egg and add the flour, parmesan cheese, parsley, minced garlic, and black pepper. Stir until combined.
Heat a non-stick frying pan over medium heat and add enough olive oil to coat the bottom.
Form the zucchini mixture into small patties and carefully place them into the pan. Cook for 2-3 minutes on each side or until golden brown.
Once cooked, remove the fritters from the pan and place them onto a kitchen towel or paper towels to drain the excess oil.
Make the tzatziki sauce by mixing together the Greek yogurt, grated cucumber, minced garlic, olive oil, lemon juice, salt, and pepper in a small bowl.
Serve the zucchini fritters warm with the tzatziki sauce for dipping.