Default [Q] How to root Asus zenfone 4 A400CG ?

I follow the exact steps as mentioned in the this thread.
But it didnt root my phone. I just bought this phone 2 days back and it has android version 4.3 with guaranteed upgrade to 4.4 kitkat.
after unboxing its firware updated twice.
the thread I used contains root file for v4.2 and there is a mismatch with the version.

I tried with Farmaroot.apk but it also didn't work.
How can I root this phone ??