Zephirin wasn't even that bad of a guy. He was - in his own way - doing what he thought was best for his people. He was an antagonist rather than an outright villain and mutilating his corpse would have achieved nothing of note.

Haurchefant is incredibly overrated in my opinion and I feel as though a lot of his fans simply let themselves be whipped into a frenzy. Yes, it was sad that he died - but it would be incredibly unrealistic to completely change the leadership of an entire nation without someone perishing on our side of the battle.

Making it be a minor NPC would be silly, too - since that would just be a cheap cop out.