Time to see if Zenkichi really CAN'T die even if he's killed.
Because, y'know, Shirou Emiya really wants to know.
Also, does anyone else think that Zenkichi looks like Unzen when he goes crazy? It's that weird glare he gets...
Spoiler:
One thing that should be remembered is that Zenkichi's the odd-one-out in the council, as far as his abilities go; he's strictly average, and not a genius like the others... but the reason that the Flask Plan seems interested in him, as revealed back in Chapter 31 or so, is because he's normal but at the same time seems to embody the very essence of the Flask Plan - the ability to not just become abnormal, but to excel in a way that innate geniuses tend to do in one subject... except that it can be passed on, and may allow for development of skills in many areas.
Abnormals here seem to be the equivalent of Idiot Savants, more than well-rounded geniuses like Medaka; the 13's all have one thing they're good at, and exceptionally so, but at the same time have serious weaknesses due to their overspecialization. Medaka's the closest thing to a 'perfect' Abnormal, at least from what we've seen so far... and yet Medaka's brother is implying that Zenkichi may have even more potential than Medaka acknowledges with her 'everyone is equal, as long as they're willing to work hard' philosophy.