I'm missing the concurrency model.

For what it's worth, the concurrency model is very similar to the one in Go. Zig has std.Io.Queue instead of channels, std.Io.async and std.Io.concurrent instead of the go keyword, and switch over std.Io.Select instead of the select keyword. There are lots of resources on concurrency in Go, and the learning semantics would carry nicely over to Zig.