1/2 cup chopped cilantro, plus whole sprigs, for garnish
In a large skillet, heat the olive oil until shimmering. Season the chicken with salt and pepper and cook over moderately high heat, stirring, until golden, about 5 minutes. Add the onion, curry, cinnamon, cayenne and 1/4 teaspoon of pepper. Cook, stirring, until fragrant, about 1 minute. Add the stock and simmer until reduced by one-third, about 10 minutes. Add the diced red pepper and zucchini and simmer until tender, about 10 minutes. Add the chickpeas and cook for 1 minute longer. Season the curried chicken with salt.
Meanwhile, in a small saucepan, bring the water to a boil. Add the couscous and 1/2 teaspoon of salt, cover and let stand for 10 minutes. Fluff the couscous with a fork, then add the chopped cilantro and toss. Transfer the curry to a serving bowl, garnish with the cilantro sprigs and serve with the couscous.