This hack is for huge money and huge credits....
Download this file first ....
1. Make sure your phone is rooted! and download this file
2. Go get the root explorer! (Android play store)
3. Go start Contract Killer Zombies and finish tutorial! (So there will be a save file)
4. Close your app completely! (I rather be on the safe side)
5. Go to download the save file from the link above!
6. Extract the file using root explorer!
7. Go back to the main page of root explorer! (The whole system)
8. Go to location--> Data\Data\com.glu.android.zombsniper\files\default\
9. Find the file: savebh.dat
10. Delete that file!
11. Go back to the folder where your file which you extracted on point 6!
12. Copy that savebh.dat which you extracted!
13. Go back to Data\Data\com.glu.android.zombsniper\files\default\
14. Paste the file there.
15. Now exit the root explorer!
16. Go and PLAY your game!
17. Join RK world for more cool stuff
For any problems , leave your comments...