Place the couscous in a large bowl. Bring 2 cups of lightly salted water to a boil. Pour the water over the couscous and cover with plastic wrap. Let sit for 10 minutes. Uncover and fluff with a fork. Meanwhile, heat the oil in a skillet over medium heat. Add the onion and zucchini and cook until lightly browned, about 5 minutes. Add the zucchini and onion, along with the remaining ingredients, to the couscous and mix well. Season with additional salt and freshly ground pepper, if desired.