Has Zoro ever said that he wants to become the 'strongest ever' or even the 'strongest man in the world'? If he wanted to, he would've never restrained his final goal to just the WSS. He would've straight up made his goal to be the WSM. Who would he even beat to become the strongest ever? Mihawk is weaker than Primebeard by manga facts.
Unless you think that Zoro fights Imu (if he/she's a fighter) or a Blackbeard with potentially 3 of the strongest devil fruits in place of Luffy, how do you think he'll even become the strongest?
When Mihawk asked Zoro for the reason he wants to fight, Zoro replied "To become The Greatest"!
Also Zoro gained interest in Defeating Mr. 1 the moment he heard the Sound of a Blade (His DF)
He said that he wants to Surpass anyone who holds a Blade, even though Mr. 1 himself said that he is NOT a Swordsman
You think Oda would make his Character say this & then give Blades to Roger, Rayleigh, Shanks, WB, BM, Shiki, Rocks ... etc but make him end up weaker than them ???
Also Zoro said he will become such a Great Sword Master that his Name will reach Heavens so clearly Swordsmanship is simply his Fighting Style of choice, his Real Dream is becoming so Strong that even Heavens hear about him
And in another Chapter, he stated that his Dream is also to Cut Everything & Anything
If Zoro was only interested in Swordsmen then why did he show the Desire to Cut Kaido who is called "Strongest Creature"?
And doesn't have a Blade
Not to mention that Oda confirmed that Ryuma is Zoro's Inspiration & we know that Ryuma was known as Holder of Strongest Warrior's Soul. Why didn't Oda say Swordsman's Soul there? Why did he choose "Warrior"? Because it's about being Strongest & not just a Swordsman
Plz let me ask you, if Oda wants to create a Character who is supposed to become Strongest Ever, what Fighting Style do you think he will choose for him? Obviously Swordsmanship + Powerful Spirit (Haki)
Shanks became Yonko & Rivals likes of WB, Kaido & BM without any DF, with just One Arm
How do you think he Achieved that? Obviously with Swordsmanship + CoC
Zoro is gonna be Strongest Warrior
Teach with 3 DFs is for now an Imaginary Character, no need to discuss him yet
And Im-Sama is Unknown, it's possible he have Broken Hax Abilities or have Weapons of Mass Destruction ... etc
But as a Warrior, both Luffy & Zoro will be Superior than him