Grate zucchini and toss with salt. Let sit in a colander for 10–15 minutes, then squeeze out as much liquid as possible using a clean kitchen towel.
In a bowl, mix zucchini with egg, flour, Parmesan, green onions, and pepper.
Heat olive oil in a skillet over medium heat.
Scoop tablespoon-sized portions of batter into the pan and flatten slightly. Cook 2–3 minutes per side until golden and crisp.
In a small bowl, mix yogurt, lemon juice, and zest. Season to taste.
Serve fritters warm with the dipping sauce on the side.