In a dish or a large sealable plastic bag, combine all the ingredients. Add the tofu, mushrooms, bell peppers and zucchini and toss to coat with the marinade. Cover the dish or seal the bag and refrigerate for 4 hours, or overnight.
Preheat the grill, setting the burners to high. Oil the grate.
Thread the tofu alternately with the vegetables onto the skewers. Season with pepper. Reserve the marinade.
Reduce the heat to medium. Place the skewers on the grill and cook, turning often, for about 10 minutes, or until the tofu is well grilled.
In a saucepan over high heat, bring the reserved marinade to a boil. Serve as a sauce. Garnish the skewers with the green onion and the cilantro. Serve with couscous or rice.