Place each chicken breast in a large zip-top bag.
Using a meat mallet, pound the chicken to an even ½-inch thickness.
In a large zip-top bag, combine olive oil, garlic, thyme, oregano, salt, black pepper, and lemon zest.
Add the chicken breasts to the marinade.
Massage the marinade into the chicken until evenly coated.
Seal the bag and place it in a bowl to prevent leaks.
Refrigerate for at least 4 hours or overnight for maximum flavor.
Preheat the grill to high heat and lightly oil the grates.
Remove the chicken from the marinade and place it on the hot grill.
Grill for 2–3 minutes per side, or until fully cooked and the internal temperature reaches 165°F (74°C).
Transfer the Best Grilled Chicken to a serving platter.
Let rest for 5 minutes before serving.