It doesn't fix use-after-free, double free().
There is some aphorism about perfection, the enemy of good, and some way in which they relate. It is relevant to understanding "why Zig?"
Object Pascal and Modula-2 dialects already offer better than Zig memory "safety", so "Why Zig" indeed.
I am all for any language that helps reduce C's usage, including Go, even when I dislike its design decisions.
Now Zig, if it doesn't fix what are about 60% of yearly expenses fixing security exploits, according to Google and Microsoft security reports, then one needs to analyse how much is it worth actually.
https://youtu.be/Gv2I7qTux7g
C but with the problems fixed.