When downloading a new update for Zombie's Retreat 2, you can transfer your save files to avoid having to start over from scratch.
PC/Windows:
Open the folder of the OLD version of ZR2, click on the www folder, find the 'save' folder and copy EVERY file within that folder.
Open the folder of the NEW version of ZR2, click on www folder, find 'save' folder and paste your copied save files into that new folder.
Android:
Do NOT delete the old version of ZR2!
When installing the new version, your device will overwrite the old files and automatically carry your save files over to the new version.
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Thanks for playing Zombie's Retreat 2!