In a medium bowl, whisk together all the ingredients for the marinade - olive oil, minced garlic, balsamic vinegar, lemon juice, oregano, parsley, paprika, cumin, onion powder, salt, sugar and black pepper. Add pounded chicken breasts to the marinade and use either a Ziploc bag, or bowl with a lid. Marinate for 4 - 8 hours or overnight in the refrigerator.
Remove chicken from fridge, and allow to sit at room temperature for at least 20 minutes. In a skillet, over medium heat, add chicken breasts and leave undisturbed for at least 3 - 4 minutes, or until brown on one side. Flip the chicken, cover skillet and repeat until done. Or, bake in oven on 400 for 18 - 20* minutes, or until the chicken is cooked through and no longer pink. Cooking time will depend on the thickness of the chicken breasts. Once done, move to a cutting board, allow to rest for a few minutes and slice.