Pulse fresh parsley, garlic clove, and thyme and lemon zest in food processor until coarsely chopped. Add Italian dressing. Pulse just until blended. Pour over chicken in a shallow dish; turn to coat both sides of each breast. Refrigerate 30 mins. Heat grill to medium heat. Remove chicken from marinade; discard marinade. Grill chicken 5-7 mins on each side or until done.