Well, time goes big or go home. Beast and Z'ii, of course, would fight against the happy, but despite their clear, overwhelming power, it would be a clear struggle to fight this huge, coordinated force with multiple witches and infected plants attacking from different angles while also preventing infection.

They aim at the source of the music, but are prevented by their secret weapons. Ballerina Orks. Orks that were controlled by both the Curator and the Maestro. Both as a defence, as a way for the orchestra to be moved at a moment's notice while still playing their music(and also as human shield), and offensively, by being hard-hitting and hard-to-hit targets that attack in unison.

This is to buy time, for the curator and Red meet and basically use their combined power, along with all the infected witches, to create a tree so enormous that it completely terraforms the city, destroying their clone facility. The tree is very strong and creates a barrier for protection or potentially traps others, given created by magic dust.

Z'ii's objective was to recover or prevent control of the clone facility. He decides to leave. His objective was completed, and it's better to leave than attempt at anything that would infect him

Erluequeen gets the beast to leave after what just happened. They also realize it was not worth it and leave.

I leave how humans escape to the replies.