In Shanks's fight against Kid, he used a very peculiar form of swordsmanship:
He used a slash that did not cut.
I believe that this is one of the strongest forms of swordsmanship, as evidenced by Koshiro's words.
Shanks has a blade that cuts only what he wishes it to cut. So much so that he has learned how to cut people without leaving an external wound, via internal destruction haki.
Mihawk, the WSSM, surpassed this style of swordsmanship, as evident by his title. Therefore, Zoro too must surpass internal destruction swordsmanship. I believe that this will happen against the sword gorosei.
We've seen Shiryu actually slash people, so I doubt he uses this style. Rather, I think Shiryu will be what Koshiro talked about when he mentioned a blade that hurts everything it touches. But the Sword Gorosei on the other hand very well could use this style.
I think this is the case because he, like Shanks, does not have a black blade, despite obviously being a master swordsman. The reason why Shanks and the Sword Gorosei don't have black blades is because they don't need them. Their swordsmanship isn't dependent on the hardness of their blades as they rely on internal destruction haki.
Overall, I think that the sword gorosei will be the greatest fight Zoro will ever have, at least apart from Mihawk, assuming Oda will make them fight. Due to his internal destruction powers, the Sword Gorosei will be able to crack and damage Zoro's swords. In order to win, Zoro will likely need to learn how to fix the damages in his swords by
forging them into black blades.