While I agree I dont see it eating up that much exp to gain less tthan the initial test when taking it to a factor of 6.
While i dont know the actual number of zombies that appeared i can go make a controlled test and copy the world if needed where i know the exact number of zombies i created using a spawn egg.
I gave it some time and it uninstalled, after a reinstall I was able to get the game to run. Before this update happened my kids had purchased a skin pack (super cute something) from the store on 9/2/202. Once the game updated is when it started crashing, not sure if it's connected or not. If you can not reproduce it, close this issue.
Thanks.