Marinate the chicken: Combine olive oil, lemon juice, lemon zest, and garlic; marinate the chicken for at least 2 hours.
Prepare the croutons: Toss ciabatta cubes with olive oil, parsley, and garlic; bake until golden and crisp.
Grill the chicken: Cook the marinated chicken on a grill until done; let it rest, then dice.
Make the dressing: Whisk together mayonnaise, buttermilk, Parmesan, garlic, lemon juice, Dijon, and Worcestershire sauce.
Assemble the salad: In a large bowl, combine chopped romaine, grilled chicken, and croutons; toss with the dressing and top with extra Parmesan.