Place chicken pieces in large baking pan. Be sure not to over-crowd the chicken.
Whisk together the vinegar, lemon juice, mustard, garlic, salt, and pepper. Then whisk in the oil. Pour over the chicken pieces and coat. Cover and refrigerate for at least 2 hours and up to 1 day turning every couple of hours.
Preheat oven to 400 degrees and roast uncovered for approximatly 45 minutes. Using tongs, transfer chicken to a serving platter and keep warm.
Skim the fat off the top of the sauce that remains in the pan. Put the sauce in a sauce pan and cook on low to reduce to half - about 8 minutes. (I just put the roasting pan on top of the stove on low heat and reduced in the pan - anything not to dirty another pot.)
Pour the sauce over the chicken and top with parsley and lemon zest.
NOTE: I sprinkled parsley flakes on the chicken before roasting. And I didn't use the lemon zest because my family isn't a fan.