Pre-heat the grill. In a large mixing bowl, combine the olive oil, garlic, vinegar, zest and juice of lemon and kale. Season with salt and pepper and gently toss until the kale is evenly coated. Carefully lay the kale side-by-side in a single layer on top of the grill and grill until crispy, about 2 minutes. Turn over and grill on the other side for another 1-2 minutes. Pile the kale in a big stack on a large plate or cutting board and serve immediately.