Zyxel NBG6602 and OpenWrt

Hello!

My son got a new cheap router called Cocraft NBG6602 made by Zyxel. I noticed that it uses OpenWrt with Zyxel's modifications and was wondering if it were possible to switch the firmware to clean OpenWrt?

Firmware:

ftp://ftp2.zyxel.com/NBG6602_co/firmware/V1.00(ABIL.0)C0.bin

/etc/openwrt_release

DISTRIB_ID="OpenWrt"
DISTRIB_RELEASE="1.00(ABIL.0)b6"
DISTRIB_REVISION="unknown"
DISTRIB_CODENAME="barrier_breaker"
DISTRIB_TARGET="ramips/generic"
DISTRIB_DESCRIPTION="OpenWrt Barrier Breaker 1.00(ABIL.0)b6"
DISTRIB_TAINTS="no-all"
DISTRIB_MANUFACTURER="ZyXEL"
DISTRIB_PRODUCT="NBG6602"
DISTRIB_HWREV="A0AA"
DISTRIB_MACQTY="4"

Extracted firmware:

https://drive.google.com/open?id=1GpLwtR9SAn763xmj8_0rb3b1_kRIRF4V

Not listed in the ToH := not supported.