Pre-TS Zoro was known for getting very Injured & Bloody against many Opponents
But Post-TS Zoro hardly got Injured badly, it was actually after +400 Chapters that Oda finally gave him a Serious Injury (Against Killer)
However it still wasn't similar to Pre-TS Zoro Situations
This week, you got your Answer
It's because only Two Yonko combined can manage to Heavily Injure Post-TS Zoro
This is why Fujitora saved Doflamingo
And this is why Zoro was Absent in WCI Arc
And why Oda didn't allow him to meet Kaido in First Act
And why he added Big Mom on the Roof
Actually if you think about it, Big Mom's Sole Contribution in this Fight was help Take Down Zoro
Other than that, she simply delayed the other Four in fighting Kaido
Plot demands Zoro to be Nerfed always so Luffy can Shine