Some of the fans seems to misunderstand about Zoro and the hardwork topic.
Yes, Zoro is a poster boy of a hardworker. But if one doesn't have enough talent, no amount of hardwork can make one reach the top.
If hardwork alone matters, then older characters will always win because they have longer time to train. There are a lot of muscular characters who is older than Zoro, but they're just a fodder or low level peeps.
Talent decides one's ceiling. Hardwork decides how fast you are reaching that ceiling. Zoro is a hardworker, but he is also a very talented character (born with CoC, is super handsome, reached Emperor level in his twenties, etc).