Disclaimer: Only for those who are ok with save scumming this one. This is not a comprehensive guide.
For anyone playing the Steam port, my personal recommendation would be launching, first, Ubisoft Connect, clicking on your profile in the top left corner, and navigating to Settings. Disable the box "Enable cloud save synchronization for supported games".
Next, launch a new survival session in Zombi. After turning on the generator for the first time, sleep in the bed to initialize a save. Quit the game.
Open up your explorer and navigate to the following directory:
C:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher\savegames\5ed8b940-0e3a-4013-9cbf-b3ab744622fb\1832
Here, you should see 1.save, 2.save, 3,save, 4.save, 5.save, 6.save. It is my understanding that 1-3 are tied to normal difficulty or chicken difficulty, and 4-6 are tied to the survival difficulty.
What I would recommend is that every time you save in a bed, you make a copy of 4.save, 5.save, and 6.save (plus the upload variants), and if you die, you simply delete the old files (along with the ones queuing to upload to the cloud if they appear), and you replace them with your backups.
I hope this helps for any Steam users!
(If anyone else has a simpler method, please fill free to correct me!)