In a plastic container with a tight-fitting lid, combine the vinegar, oil, honey, 1/2 teaspoon salt, pepper, and chopped herbs. Shake well to combine, and set the marinade aside.
Heat a grill or grill pan over medium heat. Skewer the ingredients, pairing the chicken and onion together, the zucchini and pepper together, and the tomatoes and bread together. Brush the kebabs with reserved marinade.
Grill chicken-and-onion skewers until chicken is cooked through and onions are tender, turning often, about 10 minutes. Cook zucchini-and-pepper skewers until vegetables are tender, turning often, about 7 minutes. Cook tomato-and-bread skewers until bread is toasted and tomatoes soften, turning often, about 5 minutes. Serve skewers at room temperature. Season with remaining salt.