I already using the latest Flashtool ver 0.9.10.1 to install Flashmode Drivers & Fastboot Drivers, but there is no Xperia Z driver to choose. Am I using the wrong version of Flashtool ?Download the flashtool application which is listed in the original post.
Install the application, then run C:\Flashtool\drivers\Flashtool-drivers.exe, you need to then select Xperia Z, Flashmode Drivers & Fastboot Drivers, see attached.
Then follow the instructions on how to use Flashtool, this can be found on the page link if you go to the developers website.
There is information on the Sony Website also http://developer.sonymobile.com/services/flash-tool/