I hope this is a joke right because they have never been on the same level.
Zoro beating Killer was just the tip of the iceberg. We have his performance on the rooftop and even against King. King might be dominating the battle up until now but it still didn't change the fact Zoro only have two problems against King.
King's physical strength, which is greater than Zoro. He has used it to overpowers Zoro twice. King's unique body, which is harder to damage than Kaido. Zoro still have shown a lot of power, speed and skills. Just because King is hard to damage doesn't mean he's just stand there taking attacks. He fights back and block attack. Zoro blitzed King with his death lion song. That was really impressive and continue to show just how fast Zoro is especially when he's using his top speed. Then Zoro mostly avoided King's beak laser attack at close range while enma was giving him problems.