Working two at a time, place the chicken breasts in a gallon-size resealable plastic bag and set on a flat work surface. Pound the chicken to an even thickness with a meat mallet or the back of a small, heavy pan. Remove from the bag and repeat with the remaining chicken.
Combine the flour and a pinch of salt and pepper in a shallow dish; whisk to incorporate. In a separate shallow dish, whisk the eggs. In a third shallow dish, combine the breadcrumbs, 1/4 cup Parmesan, dried basil, lemon zest, 1 tablespoon salt and 1/4 teaspoon pepper; stir to blend.
Coat the chicken breasts completely with flour and shake off the excess. Dip in the eggs and then coat with the breadcrumb mixture. Place on a clean plate or tray and set aside.
Heat the oil over medium heat in a large skillet. Pan-fry the chicken on both sides until crisp and golden, 3 to 4 minutes per side. Remove to a foil-lined baking sheet or casserole dish.
Top each chicken breast with 1/2 cup of the marinara. Sprinkle the mozzarella and 1 cup Parmesan evenly over the top. Bake until the cheese is melted and the chicken is cooked through, 20 minutes. Top each breast with a basil leaf to serve.