zig does have guard rails, they're just different approaches. zig defaults to optional types where null must be handled. and memory safety is checked through unit testing and exposing debugger memory allocators that check for different memory corruption bugs.
rust takes a shift left approach where all declarations drive safety whereas zig takes a more laid back shift right where it's expected you'll have written tests. rust will force all developers to conform to produce good code where zig requires a bit more though, i mean every dev writes test cases right?