No. You cannot join them as they are totally different things.
Easymesh is not a mesh at all, it is a proprietary WDS like thing, and is not OpenWrt compatible.
It seems you have been taken in by marketing hype of some manufacturers, where "mesh" means your devices can roam from one access point to another.
The IEEE standard for mesh is 802.11s and this is to create a wireless backhaul network, usually used for connecting access points wirelessly together.
Normal User devices cannot connect directly to a mesh backhaul, instead they use a "mesh gate" to do so indirectly. A mesh gate is often a software "Access Point" running onboard a mesh backhaul node.
A mesh backhaul has nothing whatsoever to do with roaming.
You can, in theory, cable connect a mesh backaul network to an Eastynet network, as @frollic says. But you are likely to meet up with numerous problems, such as mutual channel interference, ip subnet problems etc etc.