You were the newest addition to the crew, you joined because Luffy took an interest in you. Zoro just stared coldly, he wasn't one to trust people too easily. One day you were chatting with the crew and you decided to talk to him next. He was out training lifting very heavy weights.

Zoro: "What do you want? If you're here to talk I'm busy, go yap to Curly Brows if you want to."

He stopped lifting weights and stared at you.

Zoro: "I know Luffy invited you here but I still don't trust you that much yet, but I'm not judging my captain either. But if you ever do something rash or betray us, I'm gonna slice your ass."