Blend sour cream, water, basil, chives, and salt in a blender until smooth and pale green. Chill until ready to serve.
Put zucchini in a colander and toss with salt. Let stand at room temperature 20 minutes, then wrap zucchini in a kitchen towel and twist towel to wring out as much liquid as possible. Transfer zucchini to a large bowl and stir in flour, sugar, and pepper.
Beat egg whites with a pinch of salt using an electric mixer until they just hold stiff peaks, then gently fold into zucchini mixture.
Heat 2 tablespoons oil in a 10-inch nonstick skillet over moderately high heat until hot but not smoking. Working in batches of 5, spoon 2 tablespoons batter per pancake into skillet, flattening slightly with back of spoon. Cook pancakes, turning once, until golden brown, about 3 minutes total, transferring as cooked to paper towels to drain and adding more oil to skillet as necessary.
