In a small bowl, mix together the lemon juice, lemon zest, orange juice, orange zest, minced garlic, olive oil, chopped parsley, salt, and pepper to create the marinade.

Place the chicken breasts in a large resealable plastic bag or a shallow dish and pour the marinade over them. Seal the bag or cover the dish, and marinate in the refrigerator for at least 30 minutes (or up to 2 hours for more flavor).

Preheat your grill to medium-high heat.

Remove the chicken breasts from the marinade and place them on the preheated grill.

Grill the chicken for 6-7 minutes per side, or until the internal temperature reaches 165°F (75°C) and the chicken is no longer pink in the center.

Transfer the grilled chicken to a plate and let it rest for a few minutes before slicing.

Garnish with additional lemon zest and chopped parsley if desired, and serve hot.