Root for Xperia Z3 D6616
kingroot 4.1

http://forum.xda-developers.com/android/apps-games/one-click-root-tool-android-2-x-5-0-t3107461

if you want to remove king user and replace it with super su

follow these steps

http://www.w0lfdroid.com/2015/05/How-to-Remove-Replace-KingUser-KingRoot-with-SuperSU.html

install dual recovery by nut's (twrp,cmw,philz) using windows pc/make sure you are up to date with the drivers for xperia z3