Let's make comparisons:
1. Luffy and Lucci clashed equally once, Zoro and Lucci have been clashing with none overcoming the other for more than ten chapters.
2. Luffy was dodging Lucci while sleeping, Zoro is huffing and puffing.
3. Lucci described Luffy's power as overwhelming; as of now, he's (per his own words) satisfied with taking his number two down, confident on doing so, while Zoro expresses Lucci can't face Luffy with such level of power.
4. Luffy and Lucci were equals (and Luffy won) back in Enies Lobby, where Luffy would take Lucci's menace so seriously he'd not even take his eyes off him. Meanwhile, current Luffy casually warns Lucci not to get salty and go after weaker people since he knows he can't defeat him. The treatment Luffy gave Lucci in Enies Lobby compared to how he treats him in Egghead show clear superiority; Lucci is no threat to Luffy anymore, unlike back then.
5. Luffy actually managed to physically subdue Lucci many times during their skirmish. After who knows how many chapters of clashing, Zoro not only hasn't overwhelmed Lucci the way Luffy did, but is unable to get past his hands. Meanwhile, after their initial callback to Enies Lobby punch-clash panel (which followed Lucci's inability to shigan Luffy), Luffy sent Lucci flying to a wall and rocketed him (an insane power, according to Lucci, while he treats Zoro as a liablity for his crew).
Luffy ragdolled Lucci casually; Zoro can't get pass his hands. Lucci described Luffy's power as insane while white-eyed, spitting blood and losing consciousness; Lucci treats Zoro as an acceptable prey since he can't take the emperor down and as a burden; Luffy actually offers Zoro his help while Zoro notices Lucci waited for backup to fight again and diminishes Lucci's power as unfit for his captain (while Lucci saying Zoro may be right).
There's no way any sane person compares Luffy versus Lucci and Zoro versus Lucci and doesn't see Luffy's superiority. To summarize:
—Luffy and Lucci clash equally once; then Luffy obliterates him to the point Lucci admitting he has an insane strength. On the contrary, Zoro and Lucci have been clashing equally for lots of chapters.
—Luffy casually states Lucci can't defeat him and he better not be salty about it and even offers Zoro his help; Lucci himself admits Zoro may be right regarding his power as insufficient to fight Luffy, therefore conforming with his second as an achievable prey.
—Lucci doesn't try to fight again until Luffy is occupied with Kizaru, as Zoro notices; and, instead of treating Zoro's power as insane, he mocks him as a burden that will slow his crew down.
I mean, for real guys. It can't be more obvious: Luffy, Lucci and Zoro all know who is the strongest of the three, hence why Luffy states so in front of Lucci, hence why Zoro deems Lucci's strength as unfit for his captain, hence why Lucci conforms with second fiddle. No need to overcomplicate this.
