Uchiha bros win this. All they need to is take out Onoki. Once Onoki dies this fight is definitely their victory as:
-Jinton is the only thing that can get past Susanoo.
-Edo Itachi is here to back him up.
Taking him out shouldn't be so hard since Sasuke has multiple moves that are oneshots when they land, and two of them can't be evaded by Onoki. Susanoo Arrow and Amaterasu.
Mei's mist isn't going to save her from the bros since Katon can evaporate it, and she won't make it too thick as her comrades won't be able to navigate through it, neither will she, Zabuza had special skills so he could get around in the mist.
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so I see no reason why its a factor against the Uchiha bros.
Gaara gets killed by Enton arrows. If he gathers enough sand, he might be able to block it, but due to the speed of the arrow, Gaara can't get enough gourd sand to be able to block the arrow and tapping the ground to call a defense will only lead to it getting ripped through effortlessly, just like Madara's
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did, and they have far less piercing power than an Enton arrow.
With Onoki and Gaara gone. Mei, Ay and Tsunade have absolutely nothing to get past Susanoo with.