A first commander alongside very highly portrayed YC2 have been getting clowned by someone like Marco for last hour while Zoro was momentarily stopping Hakai with huge shockwave, cutting Kaido's scales all while overpowering his twister, and scarring him with most of his bones broken and stamina depleted.
If anything, it's the First Commanders who need to prove themselves to be close to Zoro's level- and yes, that includes Katakuri after beating whom Luffy was neg-diff material for barely sober, base Kaido.
From what they've displayed, they're losing mid-diff. Except Marco (whom I consider same level) and Ben (whom I consider bit higher)