strongest "swordsman"
also explicitly mentioned "swords skills"
there are devil fruits haki speed durability etc to take into account
with zoro and sanji they have 2 parallels that put them as dead equals ( the biggest is a century of draws)
if you want to believe mihawk is the strongest overall sure take it , he will still be weaker than zoro's equal at the end
So much yapping lol.
Oda simply said Mihawk is the strongest , superior to Shanks in swordskill.
Swordskill do involve Haki.
And what is zoro's equal? Lol.
Zoro feature all three kind of Haki and 2 advanced application on top of that.
Sanji is only 2 Haki confirmed and that too weak.
If you're talking about Luffy as zoro equal then that's most likely the given their arsenal.