Zero is played by Suzaku. This is their plan: Zero Requiem. To focus all the world's hate on one man, then remove him.
They have planned this from Charles' death.
Lelouch falls down to Nunnaly's feet. She is shocked to realize that this was always the plan.
To make a peaceful world where people could be kind to one another.
Lelouch's last words, that only Nunnaly can hear: I destroy the world and remake it anew.