You guys really have a hard time understanding Kaido's folkloric title.
Zoro doesn't KNOW that Kaido is the strongest, he's heard of it because it is what people say as per the narrator's own words
The narrator doesn't say Kaido is the strongest, he just states that this is what people say
Narrator stated that WB is WSM and stated that Mihawk is WSS, no such thing was ever done for Kaido.
So no Zoro isn't confirming that Kaido actually is the strongest character, he's confirming that he does have that reputation.
Unlike WB though there's no one well informed that has ever acknowledged it, no Sengoku,no Garp,no Kong,no Bigmom, just people who have never fought Kaido or other toptiers.
Reminder that Kaido couldn't take the advantage over a diminished Big Mom (no Zeus) after 3 days of fighting, that doesn't sound really worthy of being considered THE strongest pirate
This guy just comes in here to cry.
since Oda stated in a 1vs1, he is the winner. "If it is one against one, Kaido will win (translation of Anime)."
If it is one against one, always bet on Kaido (translation of Viz manga).
This is the same man who challenged the entire Navy and the Four Emperors ONLY and yet, they couldn't finish him.
It made Kaido frustrated to the point of being depressed because all he wanted to do was die. But as oda said, "No one could kill this man. Not even himself ".
His title was translated by some manga website as" Strongest Beast Alive ". It was a translation error because in the official VIZ translation, which is directly associated with Oda (and we have to pay to see the translation) , is declared as "On land, sea and air. He is the pirate known as the strongest Creature of all living things ".
And Oda used the word 'Saikyō Seibutsu (最強 生物): which translated as The Strongest Biological Being / The Strongest Creature Among All Beings. Seibutsu includes all living things in the world, including humans. The reason why free manga sites misspell Kaido's title is because the English word "Creature" has plural meanings, but in the original scan there is no ambiguity because the word 'Seibutsu' is the one being used, which is why Kaido was not given the title "Strongest Man" or anything like that, because he is simply not human.
Kaido's title isn't ambiguous at all in the japanese version, his title 100% include humans.
You can do a quick research on what Seibutsu mean:
https://en.wiktionary.org/wiki/せいぶつ#Japanese
living thing, life, organism, creature .
https://www.kanjijapanese.com/en/dictionary-japanese-english/seibutsu
seibutsu creature 2. seibutsu living things.
The ambiguity only come from people reading the English chapter and assuming the word "creature" is to be understood in the animal sense.
In japanese it clearly mean Kaido is the strongest living organism/thing and quite obviously humans are living things.
Kaido's title 100% put him above any human alive in the series, the only way Kaido isn't the strongest character is if his title is fake in the first place or if someone surpass him in the future.