For soy dipping sauce:

Mix vinegar, soy sauce, sugar, and a pinch of red pepper

flakes in a small bowl until sugar is dissolved. Set aside.

For fritters:

Place zucchini in a colander set in the sink and toss with 1/2 teaspoon salt.

Let stand 10 minutes, then wring zucchini dry in a clean kitchen towel. Place

zucchini in a large bowl and gently mix in egg, flour, chives, and cornstarch;

season with salt and pepper.

Heat oil in a large skillet over medium heat. Working in 2 batches, drop 1/4-cupfuls

zucchini mixture into skillet, flattening slightly; cook until golden and crisp, about

3 minutes per side. Transfer fritters to a paper towel-lined plate; season with salt.

Serve with soy dipping sauce.

DO AHEAD: Fritters can be made 30 minutes ahead. Keep warm in a 200°F oven.