When a language has built-in support for easy binding to C, that's a positive. When other languages such as Rust offer that feature through external tools, that's not as good, since I need to evaluate which of those external tools to use (when there is more than one), and it is something else to download/install/learn and another step to add to the build process. So it looks to me like Zig handles this better than Rust does (of course, Rust has clear advantages over Zig in other areas: much more mature / widely used, and more advanced memory management.)

not nearly as attractive as inline C or direct C imports

Pfft, pretty sure you could inline C in Rust. No one was brave enough to develop said compiler plugin.

C++ close enough?

https://github.com/mystor/rust-cpp

Eh, C++ isn't really C :P

I kid, it's really impressive work.