In a Dutch oven combine tomatoes, undrained pinto and kidney beans, drained garbanzo beans and hominy, tomato paste, undrained chili peppers, onions, zucchini, chili powder, cumin, garlic powder, sugar, and, if desired, salt to taste. Heat to boiling; reduce heat. Simmer, covered, for 30 minutes. Remove from heat. Add cheese; stir until melted. Serve with sour cream and garnish with cilantro, if desired. Makes 8 servings.