+Spd or +Def Zelgius?

I would say +def. As an armor unit, having def is really important. Selfies having +spd doesn’t make much of a difference IMO.

Spd is better in avoiding and making doubles unless you have Bold Fighter fodder, which makes +Def the better option. It depends solely on how you're gonna build him

Hi!
I’d recommend the +spd one, because zelgius’ HP is still quite high even with a bane, and 36 spd when booned avoids a lot of doubles-I’d rather take a slight reduction in physical bulk than getting smashed by a booned Cordelia, Tana or Linde.
Edit: changed things about IVs.