I'm not sure how what you stated is different from writing highly performance C.

I think it mostly comes down to the standard library guiding you down this path explicitly. The C stdlib is quite outdated and is full of bad design that affects both performance and ergonomics. It certainly doesn't guide you down the path of smart design.

Zig _the language_ barely does any of the heavy lifting on this front. The allocator and io stories are both just stdlib interfaces. Really the language just exists to facilitate the great toolchain and stdlib. From my experience the stdlib seems to make all the right choices, and the only time it doesn't is when the API was quickly created to get things working, but hasn't been revisited since.

A great case study of the stdlib being almost perfect is SinglyLinkedList [1]. Many other languages implement it as a container, but Zig has opted to implement it as an intrusively embedded element. This might confuse a beginner who would expect SinglyLinkedList(T) instead, but it has implications surrounding allocation and it turns out that embedding it gives you a more powerful API. And of course all operations are defined with performance in mind. prepend is given to you since it's cheap, but if you want postpend you have to implement it yourself (it's a one liner, but clearly more expensive to the reader).

Little decisions add up to make the language feel great to use and genuinely impressive for learning new things.

[1] https://ziglang.org/documentation/master/std/#std.SinglyLink...