It's kinda weird how little people expect out of Shiryu. Fans expect Blackbeard to be > Whitebeard and Roger right? Probably even significantly so. They hype his peak form to the moon.
So Shiryu, as Zoro's main fight in the BB vs Strawhats war, should be a very big problem. I imagine Zoro will need to evolve in some way during the fight, to not get defeated. Maybe it's CoO related yes, but that doesn't dehype Shiryu in any way. It would make him a different kind of threat than someone who is stronger than Zoro in terms of pure, raw firepower. A very big deal all the same.
And keep in mind that the current Zoro is already a monster.