Zig is still "not production ready," embedded is still rough, and you might have to contribute to Ziglang itself to get any particular architecture working appropriately. That said, yes people are using Zig a little for embedded stuff:

https://codelv.com/blog/2020/5/using-zig-and-the-stm32h7-to-...

https://www.mdeditor.tw/pl/2Ap9

Xtensa is less supported. M0 might also have some issues: https://github.com/Schroedingers-Hat/xtensa-zig

I've been meaning to try it out for embedded myself; I'll let you know how it goes.