Hard Reset SAMSUNG C101 S4 Zoom

First of it via Settings menu

1. Enter Apps from screen or press Menu key.
   
2. Select Settings -> Accounts -> Backup & reset -> Factory data reset -> Reset device -> Erase everything.

Second of it is via external hardware keys by entering Android system recovery

1. Please turn off the phone.
   
2. Then press and hold Volume Up + Power button simultaneously till the screen turns up and Samsung logo blinks for two times.
   
3. Now release the Power button, but keep the Volume Up key pressed till you see Android system recovery screen.
4. Select option "wipe data / factory reset" using buttons Volume Down and confirm by Home button.
   
5. Next confirm operation "Yes -- delete all data".
   
6. After finishing this operation select option "reboot system now" from the menu.
   
7. Confirm by Home button.
   

WARNING !
Hard Reset will erase all of your data
All described operations you are doing at your own risk.