Important thing is that you can do these steps WITHOUT loosing any data! (Which I lost yesterday because of my lacking information.)
Here we go (written without tablet around, so some things can be generalised):
I did it on Z2 Tablet 511, firmware .402 (no need to downgrade as I did at the beginning...)
1. Open up your device’s “Settings”. Now scroll to the bottom and tap “About phone” or “About tablet”. At the “About” screen, scroll to the bottom and tap on “Build number” seven times. Make sure you tap seven times. You will then see a notice that you are now a developer.
2. Now you should have Developer options in the System settings. Go there, enable USB debugging.
3. Again in Settings go to Security options and allow installations from Uknown source.
4. Download Easy Root v5 here http://forum.xda-developers.com/show...php?p=53448680 (guide is there also)
5. Download Backup TA v9.11 here http://forum.xda-developers.com/show....php?t=2292598 (optional for backing up your system info if you will later unlock your phone, install new ROMs etc. But if you need just root, it is not necessary. But it is recommended so you can be sure that you can get your tablet to the default status when it was bought and you can make a complaint in case something else will break down.)
6. Connect your tablet to your pc normally. Just have your tablet switched on and use USB cabel. Let it install all drivers.
7. Run Easy Root v5 (install.bat) and your tablet will be rooted in few seconds
8. For TA backup run Backup-TA.bat. Follow instructions and save your TA files. It will be created in the folder from which you run the applications. It is compressed in one file. Save it somewhere and keep it!
10. If you want to use external card without limitations, install SD fix https://play.google.com/store/apps/d...=nextapp.sdfix
For common users who want to install apps which need root and do not want to install custom ROMs or do another tricky stuff this process is enough. Enjoy your tablet now .
There can be maybe some problems with drivers. Then you can try install PC Companion which should install everything for you. http://www.sonymobile.com/global-en/tools/pc-companion/
Another thing from @stress40 who had also problems rooting the tablet:
1) I used easy root tool (on windows with Android SDK installed, ADB drivers etc)
2) extract easyroot v5 onto desktop (keeping extracted files together in a folder)
3) download towelroot.apk and put in Files folder of towelroot
4) reboot phone then plug in phone and double kick install.bat (so you get the ADB message on phone) and most importantly DON'T LET YOUR*PHONE*SCREEN*TURN*OFF (mine did so was stuck at waiting for phone but as soon as I turned it on it was fine) I was rooted in a few minutes after double clicking install.bat.