In a medium bowl, mix together the mustard, vinegar and herbs de provence. Whisk in 2 tbsp olive oil. Reserve 1 tbsp. marinade for veggies.
Add the chicken to the bowl and coat well. Let marinate for 30 minutes or up to 12 hours.
Preheat a gas grill to 400 degrees, or an indoor grill to medium high heat. Whisk 2 tbs olive oil and 1/8 tsp each salt and pepper into the reserved 1 tbsp. marinade. Add the zucchini and onion (and any other veggies you decide to use) to the mix and toss to coat.
Season chicken with 1/2 tsp each salt and pepper. Thread 1 piece chicken, 1 zucchini, one section of onion, one lemon wedge and a second piece of chicken onto a 12-inch skewer. Repeat with remaining veggies and chicken.
Add kebabs crosswise across the grate and cook for 5 minutes, covered. Turn the kebabs over and cook for another 5 minutes (covered), until meat is firm and browned all over.