I don't use Zig, but I can answer your questions:

Because Zig is a better language across the board.

And that includes safety. You can have a language that doesn't do heavy static-analysis like Rust which still makes safety a lot easier than C/C++.

Memory safety is not even a flaw of C/C++, it's a tradeoff. That being said, even if memory-safety was a 'feature' (rather than a tradeoff, and yes, Rust did a better job minimizing the trade than GC or FP languages), it's not the only feature.