Downgrading to kitkat 4.4.4 from lollipop

[nelhop]

I am very afraid of destroying my Nexus 7 by downgrading to a previous system. However, the device is now so slow that I'm making an attempt. I have looked at a number of websites for instructions and am becoming more and more confused.

I was directed to find and download the factory image. I did so. After that I was instructed to put the "image" in a folder with the ADB.exe and fastboot.exe. But I haven't the foggiest notion of which of the many files I downloaded is the correct one to choose. Here are the downloads and the various extractions:

Downloaded to folder KitKat on my PC:
folder: nakasi-ktu84p-factory-9482e892.zip

Unzipped above to folder KitKat:
folder: nakasi-ktu84p-factory-9482e892

Above folder extracted contains folder:
nakasi-ktu84p

Above folder contains:
bootloader-grouper-4.23.img
flash-all.bat
flash-all.sh
flash-base.sh
folder: image-nakasi-ktu84.zip

Above folder imgage-kakasi-ktu84.zip contains:
Android-info.txt
boot.img
recovery.img
system.img
userdata.img

Please help.

Thankyou.