Lelouch arranges a meeting with the terrorists. (He wears a mask.) He wants them to switch from terrorism to actual war.
To prove himself, he arranges a demonstration of his ability to make the impossible possible: he breaks Suzaku out and throws doubt on the accusations.
Now known as Zero, the masked terrorist has held a crowd hostage, taken responsibility for killing Clovis, and broken Suzaku out.
But when asked to join him, Suzaku refuses. He'd rather make Britannia worth from inside than destroy it. He turns himself in for his court martial.