Season the chicken pieces with 1/2 teaspoon salt and the black pepper.

Heat a large 12-inch skillet over medium-high heat. Add 1 tablespoon olive oil, then add the chicken in a single layer. Cook for 4 to 5 minutes, turning once or twice, until lightly browned. Transfer the chicken to a plate.

Reduce the skillet heat to medium. Add the remaining 1 tablespoon olive oil, onion, bell pepper, zucchini, and the remaining 1/2 teaspoon salt. Cook on the stovetop for 5 to 6 minutes, stirring occasionally, until the vegetables start to soften and pick up browned edges.

Add the garlic, tomato paste, cumin, smoked paprika, coriander, cinnamon, and red pepper flakes if using. Stir constantly for 1 minute, scraping the bottom of the skillet so the spices bloom in the oil.

Stir in the chickpeas, diced tomatoes, and chicken broth or water. Return the browned chicken and any juices to the skillet. Bring to a gentle simmer over medium heat.

Cover the skillet and simmer for 8 to 10 minutes, stirring once, until the chicken is cooked through and the sauce has thickened slightly.

Uncover and simmer for 1 to 2 minutes more if you want a thicker sauce. Turn off the heat and stir in the lemon juice or vinegar.

Sprinkle with parsley or cilantro and serve hot with warm pita, cooked rice, or boiled potatoes if desired.