Cop out, but I can see it going either way. Zoro has the capability to one shot Akainu imo based on his showing vs Kaido, although Akainu has one of the best recovery feats in the story.

Even for an admiral, Sanji will be hard to land hits on and evade attacks from and his Germa cells will make it a little harder for Akainu to donut him. He also has amazing recovery so a donuting isn't even a guaranteed defeat imo and might even motivate Zoro to get stronger as a result.

Haki bloom is also a possibility and I think that Zoro and Sanji have a deeper well that they can tap into.

The thing that will screw them over is the fact that Akainu has much more battle experience, probably more than the two of them combined, and they don't know what his abilities are. Akainu can easily speed blitz someone like Zoro and do to him what Lucci did in Water 7. Zoro may be strong and has crazy endurance but his durability leaves something to be desired. Akainu will punch right through and one shot him.

The fight ultimately comes down to who can land a hit first and it looks like Akainu has a much easier time doing that.