Sony Flashtool 0.9.18.6
Naming convention: Typically Xperia_Z_C6603_10.7.A.0.228_Generic_UK.ftf. The version number (10.7.A.0.228 is Android 5.1.1) indicates the build.
If you don’t already have Java 8 32-bit, download it from the official Oracle archive. After installation, set the JAVA_HOME environment variable pointing to C:\Program Files (x86)\Java\jre1.8.0_xxx. Sony Flashtool 0.9.18.6
The Flashtool log window shows output:
18:06:21 - INFO - Processing loader.sin
18:06:22 - INFO - Loader : S1_Root_7054
18:06:24 - INFO - Flashing data
Do not disconnect. Flashing takes 3–10 minutes. You’ll see: Naming convention : Typically Xperia_Z_C6603_10
18:08:45 - INFO - Flashing finished.
18:08:45 - INFO - Please unplug and start your phone.