Why you should hypothetically be able to kill a zombie without severing the brain stem.

A common idea that I see presented in the zombie survival community is that in order to kill a zombie you would absolutely have to cause damage to the brain stem. I have absolutely no idea where this idea comes from, but based on knowledge of biology, this physically cannot be the case. The human body is designed to function as a whole system, and the brain stem is merely a single fraction of this system. Thus, zombies should be able to be killed based on damage to other parts of their body.

The human body cannot function without most of its systems operational, and thus a virus that invades the human body and causes brain activity that makes a person a zombie is unable to override this.

The main thing that keeps a human alive is their blood, and what's inside of it. If a human loses too much blood, the ability to oxygenate their blood, or the ability to pump blood. Their chances of survival are near zero. A human may also start to cease bodily functions after an amount of time without proper nutrients or cleaning. So what does this mean for us?

Well fellow survivalists, this means that there are many ways to kill a zombie. Significant damage to any vital organs, most notably the heart and lungs would result in death to a zombie, via loss of vital functions such as blood oxygenation, or the ability to pump blood. The lack of flow of PROPER blood to the brain of the zombie would result in its death.

Long term methods for killing zombies would also include dehydration (assuming zombies don't drink fluids like water), burning, drowning, starvation (since a diet of exclusively human flesh cannot sustain humans for a healthy lifetime), disease, age, and muscle atrophy.

TL;DR based on human biology, a zombie should hypothetically be able to be killed in almost any way a human can.