Zoro is using two swords against Kaku (it's called Nitoryu)
-This is Oda telling us one more time that Zoro is the number 2, who is closer to 1, so 2=1, almost the same thing
-Meanwhile Lanji is number 4, who is too far from 2, even more from 1 (even tho it's basically equal to 1)
I hope you guys understood, i know it's complex... Well, thats Roronoa Zoro for ya