You can’t directly open a game zip project in GDevelop web version.
There is a “Open with Google Drive” option that you can try (I have no idea what it does, but I suppose you can drag a zip to google drive and open it from there)
Just so happened that my computer stopped working, I have a new computer but lost all the backup files. The only copy of the game is the one that I served to the gdevelop game site.
Last time this happened the wonderful people at gdevelop restored the build that I had served to their game site and accidently deleted. I am hoping that some nice programmer can restore my build to my list of games.