Zoro needs to power up, on that we agree. But I don't ever see him eating a DF. Especially when Mihawk and Shanks don't have DFs (well, some speculated Gryphon might have Gryphon DF like Shamrocks sword having Cerberus DF).
Even Fujitora, another top tier swordsman, likely lacks a DF and it might actually be the sword that has the Gravity fruit.
Zoros weaknesses, as stated several times several years ago, is that his body is ultimately human and thus only has normal human durability. He also lacks flying, agility, top tier speed, a flexible fighting style and above average CoO.
So we already know what he needs to improve. Mihawk, Shanks and Fujitora all have more or less the same weaknesses regarding bad (normal human) durability and the swordsman style not really mixing it up. At least Fujitora lacks agility and top speed, others probably better than Zoro in these areas. All three have solved the same weaknesses by perhaps being top 3 in the OP world when it comes to CoO so they simply don't take too many hits, especially the more agile ones.
I don't see Zoro ever besting them at CoO. I suppose offense is best defense could be his best solution, getting top 5 CoA & CoC would help him simply overpower whatever is thrown at him as long as he can detect it in time and counter.