Whisk all of the yogurt sauce ingredients together except for the salt and pepper. Taste, then add salt/pepper to taste. Cover and refrigerate until ready to serve, or up to 3 days.

Line a large bowl with a few paper towels or a clean, thin kitchen towel. (You can also use a cheesecloth for this step.) Place the shredded zucchini and onion inside. Add 1 teaspoon salt, and gently mix together. Top with another paper towel and press down so the paper towels begin absorbing some liquid. Lift everything up using the bottom paper towel and, over the sink, wring/squeeze out as much liquid as you can. The goal is to remove as much moisture from the zucchini as possible. Give your hands a break if needed, then return to squeezing out more liquid. You will be amazed how much liquid you wring out!

Whisk the egg, remaining 1/2 teaspoon salt, garlic, parsley, mint, dill, and pepper together in a large bowl until combined. Fold in the vegetables, and then whisk in the cornmeal, cornstarch, and baking powder until everything is combined.

Heat the oil in a large skillet over medium heat. Once the skillet is hot, scoop up around 2 Tablespoons of the zucchini mixture. Place the mixture onto the hot skillet and gently flatten with a spatula. Repeat with a few more, making sure not to overcrowd the skillet. Cook until golden brown, about 3 minutes. Flip, then cook for 3 more minutes on the other side. Transfer to a paper towel-lined plate, then repeat with the remaining zucchini mixture.

Serve warm fritters with yogurt sauce.

Cover and store leftovers in the refrigerator for up to 1 week. Reheat in the microwave, or use an air fryer at 375°F (191°C) for 3–4 minutes. You can also place them on a lined baking sheet and bake at 375°F (191°C) for 8–10 minutes.