Zero Requiem Does Not Erase the Damage
A Shared Beginning, Not a Magical Reset
The ending does not claim one assassination magically fixes racism, empire, grief, or every political conflict. What Lelouch creates is breathing room: Britannia's old order is broken, Schneizel is bound to serve Zero, the major powers have survived a common enemy, and the Black Knights can protect a peace that no longer depends on Lelouch commanding everything. The plan works because he finally builds an ending designed to continue without him.
The Mask Outlives the Man
SPOILER!
Zero After Lelouch
Zero began as a disguise that let Lelouch act without exposing himself. By the finale the identity belongs to the world instead. Suzaku can wear the mask because people no longer need Zero to be Lelouch; they need Zero to represent resistance to tyranny. That transformation is the cleanest measure of how far the rebellion moved beyond the boy who invented it.