Android M is a big Target for Asus to be completed by Q2 of 2016. Some of the device also got update but the ammount of bugs is infinite.
After looking for few weeks Asus have pulldown the update on OTA as well as in the website too.
ZenTalk forms filled of complain reports, So moderaors have only one thing to say that" There is some server issue so update is not avilable for now and there is no fixed time for the update procedure to start". We will know that the problem is in Android M not in server :D
So after a week of this cenario a new update notification apear on some Laser devices. And now i can see that the Moderator have been posted the details about new update on ZenTalk
About the ZE551ML / ZE5500ML asus is not saying anything. Its becuase this device is on the top list of BUGS. So Zenfone 2 users have to wait till Asus consider somthing about it.
Even the version are same but the new update file which is recently uploaded to Asus website is diffrent. The size of the First update file is 1.56GB and the one which is uploaded at 1/7/2016 is 1.62GB so i am thinking that there is some modificatin have done by Asus so those peoples who have already upgraded they can Dowgrade from THIS tutorial and download the new file and update again.. There might be some bug fix but as per reports the Battery drainage is still a problem.
Download LINK: ZE550KL Other Models Download Link will be Available SOON.