I don't think Zoro is "weaker" than his opponents when he fought them (Mr. 1, Kaku, Pica, King). Zoro only struggled with their gimmicks. The moment Zoro figured out how to counter them, Zoro won the fight. Like I could argue that Rooftop Zoro without Adv CoC can beat King, it's just that it's gonna take a while and more effort to do so. Hence why I put Zoro > Shiryu for now.