Cube potatoes. Peel and chop onion. Place potatoes (only if not from can) and onion in pot. Chop bell pepper and add to pot. Drain garbanzo beans and kidney beans and rinse with cool water. Add to pot. Add the tomatoes with their liquid, the tomato sauce, chili powder and cumin to pot. Heat to boiling over high heat, breaking up the tomatoes with a fork and stirring occasionally. Once chili is boiling, reduce heat just enough so chili bubbles gently. Cover and cook for 10 minutes. While chili is cooking, cut zucchini into½ inch slices. Stir zucchini and canned potatoes into chili. Cover and cook 5 to 7 minutes longer, stirring occasionally until potatoes and zucchini are tender.