Combine zucchini, mushrooms, onion, pineapple, and marinade in a bag or container with a lid. Place in the refrigerator and allow to marinate overnight or at least a few hours. Preheat gas or charcoal grill to medium-high heat. While the grill is heating, remove veggies and pineapple from the marinade (reserving some of the marinade for a sauce) and skewer them. Once grill is up to temperature, place the kebabs over direct heat and grill for about 5 minutes each side, or until veggies are tender and seared. Pour the reserved marinade into a saucepan, and simmer over medium heat until reduced into a thick sauce. Serve kebabs on a bed of quinoa drizzled with the sauce.