The Sony Xperia Z3 is finally receiving the Android 5.1.1 update in almost all parts of the world. If you happen to live in the nordic region and haven’t gotten the update yet on your D6603 variant, then this pre-rooted ROM for the 23.4.A.0.546 version might interest you.
A pre-rooted ROM is stock for the most part except for the stuff modified to get root access. As a bonus, this rooted 5.1.1 ROM for Xperia Z3 also comes with XZ Dual recovery included so that you don’t have to flash the recovery again after install the ROM.
This pre-rooted 23.4.A.0.546 ROM is developed by Pandemic over at XDA. You can download the ROM from link below and have simply flashed via any custom recovery of your choice along with a data wipe/factory reset.