Why dose he seem so angry at times?   and it seem more like he's very angry and not just normal I'm mad.

Is it the Brain Washing?  did beryl make him more angry along with him them evil

or is Zoisite just an angry person, (one time my grandma said that red headed people are more hot tempered)

OR dose he have MALE PMS XD XD XD XD XD 

        

I think it might have had something to do with Prince Endymion and Princess Serenity. I believe that h was a pretty calm guy before that but he started to become mad and soon furious with Endymion for his relationship with Serenity. Than when beryl took control and turned them all against Endy that she just kind of fed into what he was already feeling and thus we had Zoicites temper. but that's just one of many possibilitys and the one I usually go with

Interesting, but he also became VERY Mad when his face got "scared" (it was more like a little cut)