Zac looked at Amy, who was still finishing her makeup, and thought about Sage's threat. He obviously hated the situation he was in. His sister was in danger and he hated The Vipers.
But the enemy didn't know about his powers, let alone his interest in destroying The Vipers. Sage probably thought that Zac could do nothing against the faction, while he could use the young man to commit crimes and compromise him more and more.
Considering the standpoint of the mobster, the addition of Zac to The Vipers may possess some rationality. But he didn't know how serious it could be!
'If that's what you want, I'll destroy your faction from within, you old bastard,' Zac thought to himself, accepting the situation for the moment.
"What guarantee do I have that you won't hurt her, anyway?" he asked, pretending not to accept the situation so easily.