I want to second this comment.
The comparison shouldn't be with C, it should be with C++, Rust, or Zig.
The place to go is actually the C3 comparison page:
https://c3-lang.org/faq/compare-languages/
There you can see that there are very few items "in C3 but not Rust", for example. Mainly "it's a familiar C-like language".
I am also suspicious of the macro system. I'd like more of an explanation of how it works. Especially how it relates to Zig comptime, and whether it has "hygiene" problems. Hygiene to me means: can a variable name in a macro expansion refer to a variable outside of the macro? (The concern is that this could be accidental.)