Zatana actually knew a little bit of Chinese but it was not by chance that he spoke to Yun Jian in Country A's language. It was because he did not want Hu Qirui, Duan Tianyou, Ning Xia and their friends to find out about his family heirloom.
In reality, Zatana was the smartest out of the present bunch. He knew how to catch Yun Jian's attention and make a condition of exchange with what she would want.
As for Duan Tianyou, he was basically in the dumb*ss category for this matter. He was well aware of Lin Xiaochu's attitude toward Yun Jian earlier and had still forced Yun Jian to save her in a threatening tone. No matter who it was, they would never say yes to Duan Tianyou and agree to save the girl.
Right now, Duan Tianyou who was confident that Yun Jian would not agree to this Country A local and save his daughter was hearing the girl say yes. He and his friends could not help being caught in surprise.