1. In a large pot, heat the oil over moderate heat. Add the onion and cook, stirring occasionally, until translucent, about 5 minutes.
2. Increase the heat to moderately high. Add the chicken, cayenne, cumin, salt, and pepper to the pot. Cook, stirring occasionally, for 2 minutes.
3. Stir in the sweet potato, zucchini, tomato puree, water, and broth. Bring to a boil. Reduce the heat and simmer, stirring occasionally, until the vegetables are tender, about 10 minutes.
4. Add the couscous to the soup. Simmer for 5 minutes, stirring occasionally. Remove the pot from the heat. Let the soup stand, covered, for 2 minutes; add the parsley and serve.
Wine Recommendation: Soup with such a riot of flavors needs a wine that's big but simple. Try a California zinfandel here for its generous, spicy fruit, supple texture, and full body.