Combine first 6 ingredients in a small bowl; rub chicken with cumin mixture. Heat oil in a large nonstick skillet over medium-high heat. Add chicken, and sauté 3 minutes on each side. Add chickpeas and tomatoes; cook 5 minutes. Add zucchini and broth; bring to a boil. Cover, reduce heat, and simmer 10 minutes. Stir in lemon juice. Garnish with cilantro, if desired.