The crews swordsman who is also “a fighter” of the SH pirates is different from “the fighter” of the SH pirate
Why is it hard for you to swallow that zoros role is the fighter of the crew? It doesn‘t matter if he is a swordsman or not. Dude can also fight with his body which he did multiple times. Swordsmanship is just his personal fighting style. Just accept it and live on.