The typical urban myth that never comes with profiler proofs.
But apart from that the performance should be pretty much identical, after all it's LLVM that does the heavy lifting.
And was you point out, at the end of the day it is the same LLVM IR.
Or: the "optimization wall" in those languages is the same, only the effort to reach that wall might be slightly different (and this is actually where Zig and its stdlib might be better, it's more straightforward to reach the optimization wall because the Zig design philosophy prefers explicitness over magic)
https://programming-language-benchmarks.vercel.app/c-vs-rust
I understand that anytime someone brings benchmarks out, the next response points out that benchmarks are not real world use cases. Nonetheless, they are data points, and your claims are against the commonly accepted view of C being roughly as fast as C++ and Rust. If you have absolutely no data to back it up, you shouldn't expect anyone to believe you.
Zig does not do any work because it does not have smart pointers and it does not try to be safe. It tries to be explicit and predictable, the rest is my job.
BTW: This is very real, I've been profiling this and I couldn't believe my eyes. And even if they fixed it already there would be many similar footguns. You can't write performant software if you can't tell what work will be done.
It is 100% possible to use such style in Rust/C++ (and then the performance will be same or maybe even in favor of rust, it might be the case) but people usually do not do that.