In a large resealable plastic bag, combine the paprika, turmeric, cumin, cayenne, cinnamon, salt, and 2 tablespoons of the oil. Add the lamb, seal, and shake to coat. Refrigerate for at least 1 hour and up to 12 hours.
Heat the remaining oil in a Dutch oven or large pot over medium heat. Add the onion and carrots and cook for 15 minutes. Transfer to a plate. Add some of the lamb to the pot and brown on all sides. Transfer to a plate. Repeat with the remaining lamb. Return the lamb to the pot along with the onion and carrots. Add the garlic, ginger, and zest and stir. Add the broth and bring to a boil. Stir in the couscous. Remove from heat, cover, and set aside for 10 minutes. Stir in the cilantro, parsley, and olives. Divide among individual plates.
Recommended: Dutch oven or large pot
To Freeze: Omit the cilantro, parsley, and olives. Let the tagine cool, then ladle it into large resealable bags, filling each one halfway. Store for up to 3 months.
To Reheat: Thaw overnight in the refrigerator or thaw partially in the microwave. Warm in a covered saucepan over medium-low heat for 20 minutes. Stir in the cilantro, parsley, and olives just before serving.