*** YOU NEED TO REGISTER ON THE FORUM BEFORE YOU CAN ACCESS THE DOWNLOAD LINK ***
INSTALLATION INSTRUCTIONS
http://www.xperiablog.net/2015/03/17/guide-to-installing-xperia-lollipop-using-xperifirm-and-flashtool/
- Open link above and skip to the section entitled “FlashTool steps”.
- As you have already downloaded the FTF firmware file, skip to the section where you need to “Flash device”.
XPERIA FIRMWARE DETAILS
This is official stock Sony Xperia firmware.
Model: Sony Xperia Z4 Tablet LTE (SGP771)
Firmware version: 28.0.A.8.251_R15A
Region: UK (Generic) [1295-4697]
Android version: 5.0.2

Xperia Z4 Tablet LTE_SGP771_28.0.A.8.251_UK_Generic 5.0.2
Sony Xperia Z4 Tablet LTE (SGP771) Android 5.0.2 firmware - Generic UK