A
we know that the Sandia Kitetsu has the lowest grade among Zoro's swords , Wado is one of 21 , and so it Sushui and I expect Enma to be one of them at least.
while the Sandai kitetsu is not even one of the 50 , and we know that the Nidai Kitetsu is one of the 21 as well. so I imagine that it get broken , and he gets that Nidai as a third sword.
so his three swords would be of 21 great grades.
and i think the reason why Oda decided that Sushui should be taken from Zoro because it is already a black sword so he wanted that Zoro make his swords black himself.
so even if his swords are not of the highest grarde , they would be of them if he can make them black.
while the Sandai kitetsu is not even one of the 50 , and we know that the Nidai Kitetsu is one of the 21 as well. so I imagine that it get broken , and he gets that Nidai as a third sword.
so his three swords would be of 21 great grades.
and i think the reason why Oda decided that Sushui should be taken from Zoro because it is already a black sword so he wanted that Zoro make his swords black himself.
so even if his swords are not of the highest grarde , they would be of them if he can make them black.