"Authentication Integration for Windows" - Enable all users to login through FTP
Once the general settings of zFTPServer is setup and the Windows server has been configured, there is basically just one thing to do: create a group-account that is integrated with Windows. Generally, the Windows-group "Users" is pre-installed and all new Windows-accounts are members of this group.

Step-by-step guide in zFTPServer
You might want to use the %USERNAME% token when defining the "Home Directory" to allow users to have their Windows directories as home directory in zFTPServer: