Hey try this!
1. Log into the account which has the high stats
2. Go to Zombie/Multiplayer headquarters ( Don't go into the headquarters, just hover over it.)
3. On your controller, click the middle button and switch to the account you wish to dupe stats too
4. A message will pop up, spam "B" and As soon as it says Reading Data , quickly switch back to the high level account
5. Go back to "Xbox Live" (to the screen where it shows headquarters, public match and so on)
6. Click the middle button on your controller and go to "Settings"
7. Once at settings click "Network Settings"
8. Click "Go Offline" and then click "Go Online"
9. Open up WWII, you should have an error, click "A"
10. After clicking "A", press the Guide/back button (The two boxes button)
11. Switch to high level account
12. Click again and switch to the account you wish to have the stats on
13. Load up multiplayer, then go to the Scorestreak Tower in the HQ.
14. When you have loaded into the Scorestreak Tower pull out your ethernet cable then plug it back in or go to network settings then go offline then go back online.
15. Load up multiplayer, go into team deathmatch and get a kill.