I'm going against the consensus here. I don't think Zoro is as powerful as Kyoshiro (who I think is Denjiro) or Ashura Doji just yet
This is not true. It stated that everyone who has tried to has been unable to. The scabbards, to our knowledge, would not betray Oden and try to take his sword, so it's VERY unlikely those guys even attempted such a feat unless Oden let them try while they were alive.
It's clear he's more powerful than the ones we've seen the upper limits of at least. That being:
Kin'emon
Kanjuro
Raizo
Now. Let it be known that those three are the weakest scabbards we have seen - though I would suspect Kikunojo is also around that level of power. The problem for Zoro comes when we talk about Kawamatsu, Inuarashi, Nekomamushi and Ashura Doji.
Now, it is very likely Zoro is stronger than Kawamatsu, Inuarashi and Nekomamushi - given I think Zoro can push YC3 (being generous) whereas two of them had to 2v1 Jack. The problem comes when you look at Ashura Doji and Denjiro - the two strongest scabbards. IF these two are paired together, we can assume they're comparable in power (as they have been used to hype Oden's power)
I can't imagine Zoro doing this to Jack, let alone doing it as quickly as Ashura Doji did, until he masters Enma
Denjiro is hyped to be around as strong as Ashura Doji
Popular theory is that Denjiro is Kyoshiro, who did this
You get the impression that Kyoshiro > Zoro here. So assuming that theory is true, Zoro is around the top scabbards for power right now but will surpass them when Enma is tamed.
YC4/YC3 now
YC1 or thereabouts
Basically
Raizo < Kanjuro < Kikunojo < Kin'emon < Nekomamushi = Inuarashi ~ Kawamatsu < Current Zoro < Denjiro (If he is Kyoshiro) ~ Ashura Doji < Mastered Enma Zoro