Imo the duo can win high diff if they actually had an attack that would take out 4 tailed nardo. If they use hidan to distract him, being immortal and all, kakuzu could hit him with all he's got, or restrain him. But at that point hidan doesn't have anything to kill nardo on his own so maybe kakuzu could sacrifice a heart or something and hit himself while holding down naruto? The more I think about it this would be a lot easier if they had at least one powerful ass attack/jutsu.(not really sure if kakuZus multi-nature Justus would be enough, plus they'd have to hit, the 4 tailed naruto is pretty fast iirc)