Preheat the grill to medium-high heat.Thread the chicken, peppers, zucchini, and red onion onto the skewers, alternating between the ingredients.In a small bowl, whisk together the olive oil, balsamic vinegar, honey, Dijon mustard, garlic, salt, and pepper.Brush the skewers with the marinade, making sure to coat all sides.Place the skewers on the grill and cook for 10-12 minutes, turning occasionally, until the chicken is cooked through and the vegetables are slightly charred.Remove the skewers from the grill and let them rest for a few minutes before serving.Serve the chicken and vegetable skewers with a side salad, rice, or quinoa for a complete and satisfying meal.