How to update ZE551ML with root

Hello, hoping anyone can help me.

Time ago, i rooted my Zenfone 2 ZE551ML with the second method (bought it from dayone).
During official updated, the system stop installation it and get error message.

I followed a method for leave root permission and get the phone "clean".. so after that no more issue!! (after update i root it again :D)

Today ZE551ML get Marshmallow and much times passed from my last update (i stopped to update my phone from much time).
Now i forgot which method i used for get the phone "clean", can anyone help me?

I can't update by now without do something :/

Thanks :)

Inviato dal mio ASUS_Z00AD utilizzando Tapatalk