Official Marshmallow update is available for two variants of Asus ZenFone 2 Laser (ZE550KL & ZE551KL), tagged with version number 21.40.1220.1615.
Asus ZenFone 2 Laser ZE550KL has a new firmware update (version 184.108.40.2066) which implements improved autofocus speed and enhanced 3G/4G network speed. You can download this firmware via the direct download link provided below.
Asus ZenFone 2 Laser ZE550KL has a new update, version 220.127.116.119. The official changelog is quite long, though the update generally appears to improve network stability & call quality and fix issues with double tap to wake feature.