The biggest gap between swords that is possible by the way.
To illustrate how large the gap between both swords are, the only other Grade Blade sword we know? Is Tashigis Shigure. It is the lowest grade of named swords. Oda literally only ever made two of them. Meanwhile, Nusjuro very likely wields the same tier of blade as Roger, Whitebeard, Shanks and Mihawk. The higest grade.
Gonna be real man? Zoro is not getting a Supreme Grade Blade, a weapon wielded literally only by the strongest of the strong at the end of Egghead. Oda is not giving him it before Elbaf, before the final war, the moon and whatever else. Zoro would be too busted.
Plus, the only way he is getting that sword from Nusjuro is if he kills him and that sure as shit aint happening in this arc. The best you can hope for is a clash between the two and Nusjuro making some comments about Ryuma and Zoros resemblance to him.