Mu is a sensor, he will be able to sense every sort of eye power itachi will use.
He will pretty fast come to conclusion that they fight an uchiha, they fought madara together so they have intel about the abilities of the uchihas, muu will tell onoki when he feels that itachi is preparing Amaterasu and they will dodge it with clones or just flying around.
Itachi won't waste more chakra on ama and tsyukomi.
Kisame to use GSB, he needs to create a straight source of water first, but in that moment when he will use water domu, he will get annihilated by Jinton.
Doton> suiton and the most Katon attacks itachi has.
If itachi goes susanno, muu only needs to go invisible and wait until itachi is drained out of chakra.
Team iwa can make themselves lighter to gain speed, avoiding ama and other fast techniques.
Muu and onoki are very very sick, they will win high diff.