ZKK for me isn't just a Theory, it's something that has always been part of One Piece
In Ryuma One-Shot, Oda literally said that he always wanted to Draw a Dragon getting Beheaded & Samurai vs Knight Duel. And then in One Piece we clearly see Zoro represents Ryuma & Oda still have the same Idea for him, near End of One Piece, Zoro gonna Behead a Dragon & fight a Knight (Who are obviously Kaidou & Mihawk)
So the Motivation is clear, all that remained was finding Hints & Foreshadowing & Sub-Plots that benefit from ZKK.
That's when Zoro Fandom (And even some outside it who aren't Biased) were able to find Countless & Countless Hints
01. Parallel with Ryuma
02. Parallel with Oden
03. Relationship with Shimotsuki Family
04. Parallel with Shells Town (Literally Scene for Scene)
05. Parallel with Skypiea Arc (Enel & Kaidou share the exact same Fate)
06. Pattern of Power, Wealth & Fame
07. OP Newspaper (Suggesting Zoro gonna repeat Ryuma's Legend but with Eastern Dragon)
08. Enma Sub-Plot
09. Zoro himself wanting to Cut him (Not satisfied with Asura Feat)
10. Heavy Focus on Death + Shinigami Sub-Plot
11. Norse Mythology (Kaidou is Baldur whose Death gonna start Ragnarok or Final Arc)
12. Kaidou's Words regarding Samurai, Death, Warrior's Path & his Similarities with Zoro
13. Heavy Japanese Mythology References
14. Color Spreads Hints (Lot of them)
15. Goroawase Hints
16. Chapter Parallels (As this one you just added)
17. Heavy Buddhism & Hinduism References
18. Black Blade Sub-Plot
19. Sun followed by the Moon (Bink's Sake & Toki's Prophecy)
20. Even Anime included tons of Non-Canon Hints
21. The Necessity of killing Kaidou unlike any other Villain (He have both Legend of Undefeated & Unkillable too)
22. Zoro's Fight against Kaidou mirrors Luffy vs Croco Round 01
23. The simple Fact that this Arc is for Zoro Theme & should end with a Unique Zoro Scene
24. Zoro's Animal Themes
25. The Significance of Dragons
26. Revenge Symbolism
27. His Dream to become Swordsman who can Cut Anything
28. Tiger vs Dragon Symbolism
29. Heavy Focus on Sea, Land, Sky Theme for both Zoro & Kaidou
30. Villain obsessed with Power always waking up again (Morgan, Krieg, Enel ... etc)
31. Zoro's Desire to prove himself to Samurai & potentially lead them
32. Left Eye Symbolism (Which Oda decided Pre-Chapter 1)
33. Being given Fire-Cutting Technique, Adv. CoC & Enma together, which are all Anti-Kaidou Tools
34. Hell Symbolism for both Wano & Kaidou while Zoro declared himself "King of Hell"
35. Zoro's Wano Viver Card Hint & Kaidou being Number 944
And much much more ... etc
ZKK Haters ---> ThIs ThEoRy DoEsN'T MaKe SeNsE aT All