Light a grill or preheat a grill pan. In a large bowl, whisk the olive oil with the garlic, thyme and oregano. Add the tomatoes, zucchini and bread and toss well to coat. Season with salt and pepper. On four 12-inch metal skewers, thread the tomatoes, zucchini and bread, alternating between them. Arrange the skewers on a plate and drizzle them with any remaining olive oil mixture from the bowl.