How to update manual :
Software Update SOP for ZenFone 4 & 5 & 6(Eng) Download Lollipop for ASUS Zenfone 4 : Version
WW_7.3.3 (Android L)
Please make sure update software version
WW_6.6.3Download Lollipop for ASUS Zenfone 5 : Version
WW_3.23.40.60 (Android L)
Please make sure update software version after
WW_2.22.40.5 Download Lollipop for ASUS Zenfone 6 : Version
WW_3.23.40.52(Android L)
Please make sure update software version
WW_2.22.40.44