Zelgius -Atk/+def

I understand you want to give your Zelgius an other build, but I think he would be better with the same build as the black knight, since his 41 def without any skills is insanely high. With that amount of def he would be very good with steady breath, quick riposte and Aether. The black knight will also be stronger offensively so it would be better to give him an other build. However, Zelgius can run a (any offensive a skill) + bold fighter + black luna build quite well too, only a little less effective than the black knight. If you are going for the build I mentioned last, I would put him on an armor team with armor march, or give him the armored boots outside of it, since the 1 movement restriction for armored units can hurt his offensive capabilities quite a bit.