As zac, Zac is quite good in late-game team fights, especially if he manages to get a flank on the enemy. Another reason why he is so good is that he can easily bypass vision and catch the enemy off-guard.

Zac will be extremely tanky during this stage, and the enemy team will have a tough time killing him. This also means that he can act as an engager for a team and then revert back to peeling for his carries once the engagement is over. 

Once he gets three points in his Ultimate R, he will be able to use it frequently and deal a lot of damage to the enemy team at a go. He should be able to catch enemies off-guard easily, especially when using the fog of war. As zac, Zac is pretty good in the team fights at the end of the game, especially if he manages to get a flank on the enemy. Another reason why it is so good is that he can easily bypass the vision and catch the out-of-guard enemy. Zac will be extremely tanky during this stage, and the enemy team will have a hard time to kill. This also means that he can act as an engager for a team and then come back to peel for his portages once the engagement is over. Once he gets three points in his Ultimate R, he will be able to use it frequently and cause a lot of damage to the enemy team with a boost. He should be able to catch the out-of-guard enemies easily, especially when using the war fog.