In order to delete other users from the account, you must be a user with Administrator privileges
Zendesk Sell gives you a number of options when it comes to user management. One of them is user deletion. To delete a user go to the Settings > User Management screen and click on the user you would like to delete. At the bottom of the pop-up screen, click Deactivate User.
When a user is deleted, you will be able to select who should be the new owner of that user's data (contacts, leads, and deals). Please note that deleted user's emails will be purged from Sell.
When you remove a user from your account, you'll have the option of adding another user to replace their seat in the application. When you invite a replacement user, you won't be charged - the new user will simply take over the application access granted for the remainder of your billing cycle.