Neither Zoro nor Kaku was going all out. Point is Oda made Zoro vs Kaku inconclusive, and had to use a plot device(Stussy) to put Kaku to sleep when in Luffy vs Lucci's case, he showed the big gap between them with Luffy effortlessly dodging Lucci's attacks(while sleeping in some panels) and being close to KO him with one of his attacks
The first 3 pages of Luffy vs Lucci:
> Luffy uses G5, his strongest mode. Lucci uses awakening, his strongest mode.
> Luffy dodges some unnamed attacks from Lucci.
> Luffy and Lucci harden their fists, clash equally and send each other flying
The first 3 pages of Zoro vs Kaku:
> Kaku uses his strongest Rankyaku in Base. Zoro wakes up and casually blocks.
> Kaku uses awakening, his strongest mode.
> Kaku uses an upgraded version of his old named attack.
> Zoro hardens his swords and blocks whilst being pushed back.
> Zoro overpowers Kaku and sends him flying.
Summary:
Both Luffy/Lucci and Zoro/Kaku had callbacks. But these callbacks still apply as feats. Base Lucci once clashed equally with Base Luffy. Now Awakened Lucci is able to clash equally with ACoC-less G5 Luffy. After which he got stomped.
Hybrid Kaku once overpowered Zoro using Bigan and sent him flying, inflicting moderate damage. Zoro had to use a named attack that specifically increases his physical strength to overpower Bigan in the past.
Now, Kaku uses his strongest form, Awakening - the exact same form that Lucci now possesses (meaning Kaku's growth rate is confirmed to be faster than Lucci's). He uses an upgraded version of Bigan coated in CoA and Zoro successfully blocks with hardened swords. He then overpowers Awakened Kaku with a nameless attack, sending him flying.
Objectively, Zoro was much more casual against Kaku than Luffy was against Lucci. Zoro used zero named attacks and had much more in reserve than Luffy did. And once Luffy's callback with Lucci was over (which looked much worse for him than Zoro's callback with Kaku), he proceeded to stomp. So to pretend that Oda cheapshotted Kaku via Stussy because Zoro is incapable of stomping Kaku himself is disingenuous, as I'm sure we all know if Zoro wanted to stomp he absolutely could've by going all-out for one attack. Oda didn't need Luffy to use G5 to have his call-back, he could've done it in Base/G2. Meaning he used G5 because he needed it.
What did Luffy have in reserve vs Luffy? ACoA, ACoC, higher-end G5 moves. What did Zoro have in reserve? Higher-release CoA, ACoC, KOH, Asura. Zoro held back more than Luffy and looked better against a Kaku who was using stronger attacks than Lucci was, who really was barely tryna fight Luffy and was mostly aiming for Sentomaru. And in the end, Lucci looked better after the battle than Luffy did lol.
Ultimately, all of this is irrelevant as we all know Luffy and Zoro are capable of shitstomping both Lucci and Kaku. But it is interesting that Oda didn't even have Zoro use any named attacks let alone ACoC, meanwhile Luffy used one of his strongest Gears against a character with the exact same awakened form as the opponent Zoro fought. To Oda, it seems ACoC-less Base Zoro is comparable to ACoC-less G5 Luffy.