User blog comment:HanataSanchou/The Wano Country/@comment-25926617-20150418050414

My best guess is that whilst Luffy is busy eating the entire country Zoro gets out lawed and kaido/big mom send a swordsman (or maybe just a strong henchmen) and Zoro defeats him with realitve ease so the people respect him and then they bestow secret samurai techniques to Zoro where he gets stronger from. Either that or he helps the country in some way besides Kin'emon vouching for him.