In the microcontroller space, I think Zig is more of a replacement for C/C++. It's a compiled language, intended to produce optimized code that hits cost/performance targets.

Micropython and friends are well-suited for education/hobby use, protoptyping, and maybe some commercial applications that aren't sensitive to cost or realtime characteristics. But since they don't really compete with C/C++, they also don't really compete with Zig.