Not consistent at all
Zoro was stronger all the way until Skypea
EL Luffy pulled slightly ahead
Thriller Baek Zoro was stronger again
Entire poat time skip before AcoA he was stronger
Before AcoC he was stronger
Currently liffy is maybe stronger but doesn't look like it
But Sanji was low no diff for Zoro literally entire Manga
luffy has more AP, DC, lethality, better defense, better speed, more mobility, better cqc, better swordmanship in TB with shadow luffy, a stronger will, more endurance, better durability, better sensory abilities, better intuition, combat intelligence, a better style, stronger range attacks, a more diverse set of abilities, a better range of motion, more impactful attacks, better momentum in battles, less plot armor, etc
idk how zoro is even close, even sanji is better stat wise but sanji is kinda nerfed by having two roles as a chef and combatant
i think zoro has extreme high potential tho, excited for if he can leverage it against his first yonko fight when he will fight Mihawk