I actually though about it and it if you packed all the 4 zero chapters in 26, it fits well, I rarely used filler robots.
1.- Ciel revives zero, sacrifices baby elf, introductory post-apocaliptic fights
2.- Zero receives his saber by X, introduction of headquarters
3.- Zero saves the little girl with the doll, basically just zero still getting to know the refugees from headquarters, Ciel tells a big background story of why everything is so chaotic.
4.- the 4 judges are introduced, awesome fight scene with Fefnir, Zero uses his shield and gun, in this fight, blocking Fefnir's blast shots, its a long range fight.
5.- Leviathan chapter, lots of casualties, Zero uses his spear against leviathan. Copy X is introduced, one hell of a scary guy.
6.- Zero has to find out about his past in the lab he came from, lots of memories, discussion about evil X, he meets phantom in the lab, fight is tense, continues
7.- continuation of phantom fight, awesome choreography, with zero finally defeating phantom with the shield boomerang, zero finds out phantom is not that much of a bad guy, but phantom kills himself trying to kill zero.
8.-Zero decides to raid neo-arcadia, most of the chapter is him entering and ciel preparing for the worst, angered by phantom, he now faces harpuia, Zeros first real sword fight, after beating him, he now faces copy X
9- Zero defeats copy X, he saved the refugees, finally a true flashback of when zero fought wars with X, really sad because X cant fight anymore, ends with zero becoming a loner.