01 - Whisk olive oil, lemon juice, lemon zest, garlic, thyme, rosemary, parsley, salt, and black pepper in a medium bowl until well combined.
02 - Place chicken breasts between two sheets of plastic wrap and gently pound to an even thickness of about ¾ inch.
03 - Add chicken breasts to the marinade, turning to coat thoroughly. Cover and refrigerate for at least 30 minutes or up to 2 hours for enhanced flavor.
04 - Heat grill or grill pan to medium-high. Lightly oil the grates to prevent sticking.
05 - Remove chicken from marinade, allowing excess to drip off. Grill for 6 to 7 minutes per side until internal temperature reaches 165°F and juices run clear.
06 - Remove chicken from grill and let rest for 5 minutes. Slice and optionally garnish with lemon slices and fresh parsley before serving.