I hate you i really do >.>
I feel bad for you so I'm going to post my personal opinion on this matchup.
Kakuzu takes this low-mid difficulty.
Chouji's not landing a single hit on Kakuzu considering it took distractions from Ino and Shikamaru to give Chouji an opening to strike (
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). To top it all off, Kakuzu is a long ranged fighter so he has plenty of time to react unlike Asuma who is primarily a close range specialist.
Just look at how big Chouji's head is and even his eyes are a good target for raiton gian (
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). You may think Chouji can simply use his arms to block an attack like this. That is true, in no way are any of Kakuzu's elemental attacks taking down Chouji but they will definitely hurt him. Raiton gian spam will start drilling a large number of holes in Chouji's arms and make him bleed to death or render his arms unusable thereby losing the ability to punch. Gian may not have many feats but even low tier raiton attacks such as raiton enhanced kunais have been able to penetrate through rock at least few metres thick so raiton gian, being much larger in magnitude, will yield a lot more damage.
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blowing raiton gian away is a fallacious counter considering the wind blown from his wings don't have much damage output unlike gian which has a lot more power focussed into it, especially per unit area.
Meanwhile, Kakuzu can send out his katon and fuuton mask to use its smoke to blind Chouji. This would allow the real Kakuzu fused with his raiton mask to get behind him and attack Chouji from the sides.
Also bare in mind that all these elemental jutsus will cause Chouji to feel pain which will interfere with his control over his expansion jutsu. Enough hits will make it problematic for Chouji to maintain his expansion.