True if they get CoC Haki, Lanji's must be later as Rayleigh also showed Haki types in this order, weakest to strongest types:
CoO first (Lanji's specialized Haki) > CoA second (Zolo's) > CoC third (Luffy's)
Since Zolo got much later than Luffy as second, if Lanji will get CoC as third it should be after Zolo as well.
Also as Rayleigh said you can't train CoC to be stronger it only grows with your general Haki level, but people like Luffy and Shanks specialize in CoC while people like Zolo, Mihawk and Sanji specialize in CoA or CoO, so even if they are equal level, Luffy and Shanks will always have the CoC skill and talent edge over them.
Thats why Luffy was using CoC much earlier than Zolo, when Dressrosa Zolo was much stronger than Pre-TS Luffy, or kid Doflamingo, kid Ace or kid Yamato, Zolo only unlocked CoC in Wano, thats because Zolo is specialized in CoA while they are in CoC.