So, imagine you run
Zaul, Zader are good leaders as well.
So, you are fighting and someone kills your Zihilus. Why should the leader ability still work?
Doesn't make sense. So, what I'm saying is, that if your leader is killed, you lose the leader bonuses+10 speed. Demoralize is basically a Debuff which is gained when a teams leader is defeated and it makes you lose 10 speed. BUT. Since you have Zaul, once Zaul's turn comes, you use the ability called Takeover, making him the new leader, and dispel the Demoralize Debuff, which cannot be dispelled unless Takeover is performed.
1...2...3! You're dead!