Sony has released the latest Android Lollipop version starting with
the Xperia Z3 and Z2 series. The over-the-air update with build version
23.4.A.0.546 should be available for your Xperia devices anytime now.
over to Settings >> About phone>> Software updates>>
System updates to check the availability of the new stock firmware. But
for some reason if you have missed the OTA notification or, it is yet to
hit your region, do not worry as the FTF link for the OTA is available
to perform a manual installation on the Z3.
Following is a guide
to install stock Lollipop build 23.4.A.0.546 on Xperia Z3 using the Sony
FlashTool. This method is also helpful for those who have rooted their
Z3, as the OTA will be available for devices with locked bootloaders
firmware used in the guide is compatible with Xperia Z3 D6603 model.
Applying this on any other Xperia variant might brick the device.
the developer rights on. Tap on Menu then Settings and navigate to
About Phone. From there tap the build number a few times.
USB debugging on the phone- navigate to Menu>> Settings>>
developer options and check the USB debugging feature.
Ensure that your Xperia Z3 is having above 80% battery charge.
How to update Xperia Z3 D6603 to Android 5.1.1 stock firmware build 23.4.A.0.546
Step-1: Download the FlashTool file on your PC. Unzip it then install it following the screen prompts