Put cucumber, radish, and lemon zest in a medium bowl and add cheese.
In a small mason jar add lemon juice, vinegar, dill, sugar, and garlic in another medium bowl, shaking until sugar has dissolved; season with salt and pepper. Add the oil in and shake until emulsified.
Add vinaigrette and feta to cucumber mixture; toss well. Garnish with dill. Refrigerate salad in an airtight container up to 1 hour.
From Martha Stewart