I think any replacement for c/c++ will not be strictly safe from memory safety vulnerabilities, but I think both Rust and Zig go far enough to effectively nearly eliminate that entire class of vulns in production software. Rust achieves further memory safety than most with its borrow checker but in many cases that seems to be more about safety from crashing than vulns. For example, Go is not memory safe under concurrency, but there have been no memory safety vulns related to its concurrency ever.

One could also argue Rust's unsafe blocks will be harder to reason about bugs in than Zig code. And if you don't need any unsafe blocks it might not be an application best suited to Zig or Rust.