Wash hands with soap and water; ensure worksurface is clean.
Start some water boiling in a medium-sized pan big enough for strips of zucchini to fit in.
Cut the cheese into 24 chunks, set aside.
Wash tomatoes by rubbing under cold running water, set aside.
Wash zucchini by scrubbing with vegetable brush under cold running water. Slice each zucchini lengthwise into 6 thick strips (do not peel.) Blanch the zucchini strips several at a time in the boiling water for 1 minute, then drain and pat dry.
Take a skewer, and put the skewer through the top of a zucchini strip. Push the zucchini strip up the skewer a bit, then put a tomato on, then thread another fold of the zucchini on, then put a chunk of cheese on, then thread another fold of the zucchini on. Repeat until the skewer is full. Each skewer should take 1 strip of zucchini, two tomatoes and two chunks of cheese, and you should end up with around 12 skewers.
Put the skewers in a shallow baking dish.
Mix the remaining ingredients to form a marinade, and pour over the skewers. Allow to marinate covered with plastic film in the refrigerator for at least half an hour.
Cook on a hot barbeque grill for 3 to 4 minutes, then turn them over and cook for another 3 to 4 minutes. Serve hot.