Using legacy software always carries inherent risks. Here’s an honest assessment for :
Did you install the flash drivers from the flashtool installation directory. samnaction. – samnaction. 2014-04-16 11:12:45 +00:00. Android Enthusiasts Stack Exchange Xperia ZL Firmware Update (10.1.1.A.1.253) - XDA Forums flashtool-0.9.13.0
For more detailed device-specific guides, communities like the XDA Forums Xperia Blog Using legacy software always carries inherent risks