Zig async doesn't change semantics of how things are called. If something is called sequentially, it will execute sequentially with respect to itself, with or without async.

It doesn't change the semantics, the documentation says: https://ziglang.org/documentation/0.10.1/#Async-Functions

"Async functions can be called the same as normal functions." Only when you have an event loop, the order async functions are running might be different because of the scheduling, but everything else is the same.