Zink is a Vulkan driver that provides support for OpenGL(2.1-4.6), OpenGL ES on GPUs that only support Vulkan. Included in a free implementation of OpenGL, Vulkan API - Mesa
In the future, it may become a compatibility layer for new GPUs if they remove support for the already obsolete OpenGL.
Assembly in Mesa
To build Zink (also with OpenGL ES) in Mesa, you need to use these flags when building:
meson . build -Dgallium-va=false -Ddri-drivers= -Dgallium-drivers=zink,swrast -Ddri3=true -Dvulkan-drivers= -Dglx=xlib -Dplatforms=x11,wayland -Dbuildtype=release
This configuration does not include the Vulkan drivers, because different GPUs require different drivers.
Instructions for building Zink with Turnip to run GPU Adreno in ExaGear is here.