For the balsamic vinaigrette:
1) Whisk the vinegar, mustard, lemon juice, garlic, olive oil, salt, and pepper in small bowl to blend.
For the chicken:
1) Combine the vinaigrette and chicken pieces in a large resealable plastic bag; seal the bag and toss to coat. Refrigerate, turning the chicken pieces occasionally, for at least two hours and up to one day.
2) Preheat the oven to 200°C.
3) Remove chicken from the bag and arrange the chicken pieces on a large greased baking dish. Roast until the chicken is just cooked through, about one hour. If your chicken browns too quickly, cover it with foil for the remaining cooking time.
4) Transfer the chicken to a serving platter.
5) Place the baking dish on a burner over medium-low heat. Whisk the chicken broth into the pan drippings, scraping up any browned bits on the bottom of the baking tray with a wooden spoon and mixing them into the broth and pan drippings. Drizzle the pan drippings over the chicken.
6) Sprinkle the lemon zest and parsley over the chicken, and serve.