I recently found a dead rat in my backyard.  It had been dead for a while, and had begun to decay.  The stench was horrendous.   One thing you never notice in zombie media is people being repulsed by the smell of all that death.  Any "realistic" treatment of zombies should address this.  I know that over time you may be able to get used to it, and that the adrenaline required to stay alive might help you ignore it while in the midst of battle..... but the smell is going to get to you.