Slice the zucchini very thinly, preferably with a mandoline, to create even slices that become crisp when fried.
Place the zucchini in a bowl and sprinkle with salt. Let stand for 10 minutes, then pat dry thoroughly with paper towels.
Combine the semolina, cornstarch, and baking powder in a bowl.
Heat oil in a large pot over medium heat to 350°F/180°C.
Coat the zucchini slices in the semolina mixture, shaking off any excess. Fry in batches until golden and crisp, 2 to 3 minutes.
Combine the yogurt, cucumber, garlic, lemon juice, olive oil, dill, and salt in a bowl. Stir until smooth. Chill until ready to serve.
Transfer to a paper towel-lined plate. Sprinkle with salt and lemon zest while warm.
Serve immediately with tzatziki.