Its not really about Kid's level or him being weaker than Zoro
People underestimate the amount of damage Kid's(and Law's) awakenings did to big mom.
How many times have you heard people downplay Kid's awakening as "just throwing metal" or shit on these attacks merely for not having ACoA or ACoC attached to them. Fact is, if these attacks can make big mom sacrifice her life force, they are likely comparable to ACoC infused attacks.
If I were to guess, imo these attacks are stronger than Luffy's G2/G3 ACoC attacks, but weaker than Luffy's G4 or Zoro's King of hell 3 dragons.
Either this or Big Mom is actually FAR weaker than Kaido despite all portrayal saying otherwise.
Kaido would high diff Big Mom but durability wise she's a lot weaker than Kaido because of how she reacted to different falls and Gear 4th.
If I were to give Kidd and Law their just due I can agree they are perhaps a bit above Red Roc and Zoros Tatsumaki but definitely below Hiryu Kaen
I don't even think they compare to Ashura or Luffys strongest CoC punches
That move on King the final move is just on a different level
I guess it's something like this
Zoros final 3 dragon attack 100
Luffys strongest attack right now 80
Ashura 60
Luffys top CoC punches 50
Hiryu Kaen 45
Law and Kidds awakening 30
Tatsumaki and Red Roc 25