In a medium bowl, mash beans, egg whites, garlic, and cumin to a coarse texture (it should be a mixture of mashed and nearly whole beans). Stir in the zucchini and bread crumbs.
Heat large nonstick skillet over medium-high heat. Add 1 teaspoon of oil. Using 1/2 of the bean mixture, drop 4 mounds into the pan and flatten them to about 3 1/2-inch rounds. Cook for 4 minutes, turning halfway during cooking; repeat with remaining mixture. Serve with salsa and sour cream.