Laser 2[ZE551KL] Stuck on Lollipop (Unlocked bootloader)

Hello team of professionals!
First, I thank you all for your hard work and development of this device!

I have an issue updating to the latest stock room from Asus.
I had CM13 (Android 6) installed on my Asus Zenfone 2 Laser (ZE551KL).

When I heard that stock marshmallow was released I was interested in installing the ROM.

I tried for several hours to install the update and ended up bricking my phone.
I recovered it by installing the most recent stock Lollipop firmware from Asus' website.

Currently my phone has stock Lollipop with the ROM (UL-Z00T-WW-1.17.40.1531-user)
and stock recovery (attempted to do this so I could upgrade from lollipop to marshmallow)

At this time I am trying to install the most recent (Android 6) update "UL-Z00T-WW-21.40.1220.1615-user.zip" Downloaded from my device's page on Asus' site however I get errors every time I try.

I tried to update via stock android by placing the update zip on my SD card and launching from "System update file detected" notification.
The update restarts my phone, starts installing (With the little android guy) and then fails with the error:

Code:

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Can't install this M package (May 17 2015)

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Code:

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L less than 20160426 build (Dec 1 2015)

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Code:

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E:Error in /sdcard/updatefile.zip

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Code:

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(Status 7)

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Code:

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E: fota_return_code 409

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Code:

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Installation aborted(EUPDATE_BAD_PARMSE)

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When attempting with TWRP:

Code:

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Updater process ended with ERROR 7.
Error installing zip file "xxxxxxxxxxx.zip"

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:confused::(
Any help would be appreciated