I mean Luffy's CoA isn't that weak..it has improved but not to Zoro's level.
Here is how I see it
@MonochromeYoru
Enma Haki Flow Regulation --> Meaning Zoro is literally controlling his flow against Enma..winning the tug of war of Haki >>> Internal destruction
Zoro's Island sized Barriers >> Luffy's basic barriers which Zoro showed in Fish Man Island
Zoro's mountain busting Haki leak >>> Luffy's Ryou Barriers
Zoro's Mountain level explosion tank >> Luffy struggling against Ulti's head butt
Like Luffy's Haki is far above low and midd's but Zoro is just two or three tiers above.
Things that Zoro's CoA has tanked would kill Luffy.