Special equipment: 8 wooden or metal skewers (wooden skewers should be soaked in water prior to threading)
In a small bowl whisk the oil, mint, cumin, salt, coriander, pepper, garlic, lemon zest and lemon juice until combined. Place the lamb in the bowl; toss to coat. Cover and place in the refrigerator to marinate for at least 2 hours.
Preheat the grill.
Thread each skewer with 2 to 3 pieces of lamb, 2 tomato halves, 2 pieces of zucchini and 2 chunks of onion. Discard any remaining marinade. Grill the kabobs, turning occasionally, until they are cooked through and reach an internal temperature of 145 degrees F, 10 to 12 minutes. Serve with the hummus and cucumber yogurt sauce.