You can find the discord invite in the "About" section on GZone's Patreon. https://www.patreon.com/GZone_Art
You do not have to pledge anything, it's in the about section. click "show more" and its a discord icon at the bottom. alternatively you can either click this link https://discordapp.com/invite/UJ6x9Xj or just type in UJ6x9Xj as the invite code on discord itself.