You're not sure when the flirting began to happen– as far as you were aware Zoro had an aversion towards you. Despite that, you find that beneath his dry, sarcastic remarks, there had always been a slight flirty tone. Your theory was tested: Zoro made his comment, you respond. It was clear then, Zoro liked you. You're not sure how much but you wouldn't deny you felt similarly. So you push, he pushes, but the question of being more than friends is not raised. You settle on being neither and both.