With anyzig, we could create a "versionless" GitHub action to install zig. This could either be a new action altogether, or maybe, we could enhance mlugg's action to support anyzig? One way this could be done is to reserve the zig version "any" in mlugg's action to mean that it should install anyzig.
P.S. it looks like mlugg's action already supports not specifying a version, and ends up using minimum_zig_version from build.zig.zon already, so, this might already be good enough?