I’m not sure why the data recovery software isn’t working given that you can see it with a hex editor. I mean, it’s been 35 years and change since I fired up Norton Utilities, but it sounds like the data should be recoverable as long as it hasn’t been overwritten, and even then it should be partially recoverable.

Whether a partial recovery is useful depends entirely on the type of file. The zip file might be dead but there might be a recovery path there, too.

It’s not a lot of money to give it a shot, but maybe also talk to the linux users group at your closest university or posting to communities that are populated by people who get into the low level stuff. If it’s for a system that was popular at the time (Apple, Amiga, some types of PCs), you might be able to find a retro computing hobbyist community directly. We’d do stuff like that in exchange for beer when I was in college.