For Lu Xun to have risen up through the ranks, his talents and skills weren't the only determining factors. More importantly was his attitude. Regardless of the challenges that he faces, he deals with them in a calm manner, not allowing pride to get in his way. Even though Zhang Xuan's reputation is terrible, Lu Xun didn't underestimate him at all and made preparations in advance.
Before deciding on the students to send for the duel, he investigated Zhang Xuan's students in order to pick out the best combination to deal with and counter them.
Based on his investigation, Zheng Yang grew up with Mo Xiao and they practiced the spear together. However, the Mo Xiao’s talents are obviously superior to Zheng Yang, and of the countless battle between the two, it had always been Mo Xiao's victory.
This was precisely the reason why he poached Mo Xiao from his best friend, even having his friend impart him the Wang Clan's spearmanship.