Step 1 Spray a large saucepan with oil and place over medium-high heat. Cook lamb, stirring, for 7–8 minutes, or until browned. Add onions, garlic and ginger and cook, stirring, for 5 minutes, or until softened.
Step 2 Add paprika, turmeric and cinnamon. Cook, stirring for 1 minute, or until fragrant. Add tomatoes and 1 cup cold water. Bring to the boil, then reduce heat to low and simmer, covered, for 1 hour.
Step 3 Add sweet potato and dates. Cook, uncovered, for 20–25 minutes, or until lamb is tender and sauce has thickened slightly. Season well with pepper and stir in half of the coriander.
Step 4 Meanwhile, place couscous and zucchini into a heatproof bowl. Add 1 1/4 cups boiling water. Cover and stand for 5 minutes. Use a fork to separate and then fluff couscous grains and season with pepper. Serve tagine with couscous and topped with remaining coriander.