1. Put the oil in a deep, heavy skillet over medium-high heat. Cut the chicken into 1/2- to 3/4-inch cubes. Add to the skillet, raise the heat to high, and stir once or twice.
2. While the chicken browns, peel and quarter the onion and put in a food processor. Pulse until just chopped. Add the onion, cumin, ginger, and paprika to the skillet. Stir and cook for 1 minute. Add the stock to the skillet and stir with a wide wooden spoon, scraping any bits from the bottom. Cover and bring to a boil, about 2 minutes.
3. Meanwhile, trim the zucchini and slice in half lengthwise. Then cut crosswise into 1/4-inch-wide half-moons. When the soup comes to a boil, add the zucchini and the couscous to the skillet, stir, and cover.
4. Open the can of chickpeas into a small colander, rinse, and drain briefly. Add to the skillet. Cover and let the soup return to a boil, then lower the heat slightly so the soup simmers briskly for 4 minutes. Season with salt and pepper to taste. Chop the leaves from the cilantro sprigs. Stir into the soup, cook for 1 minute, and serve in soup plates.