The zip file likely contains the following components, as detailed on the itch.io project page :
Based on "First Blood" mechanics (implied by the title). GOD-KILLER-master.zip
To use the GOD-KILLER-master.zip file, you should unzip the contents, read the main rules document first, and print or digitally fill out the character sheet to begin playing. The zip file likely contains the following components,
The primary 33 MB document containing the core rules and setting material. you should unzip the contents
A 734 kB PDF outlining character actions (moves).
A 4.9 MB PDF for recording character details.