Inside the .zip is a file called DeepSpaceAdventure.pcio
This file contains everything you need to play the game. Head to https://playingcards.io and create a custom room. Click on the 'edit table' button, click on 'room options' and you'll see the option to import a room from a file. Just navigate to your downloaded .pcio file and that's it. Click 'edit table' once more to return to play mode.
We made a short video showing you how to load the game here: https://bit.ly/ggj2021HowToLoadDeepSpaceAdventure
Additional art (the fox!) by Kris