Zig doesn't offer much in terms of high level abstractions and is very manual (I'd consider it far too much pain here unless for the embedded realm) - it's a better C at best, no rival for C++'s power and software design capabilities...
Rust has serious pain points when you consider the borrow checker and want to do complex stuff asynchronously, there's a big learning curve here, also not in every realm is it crucial to have memory safety (a desktop computer game is not flight control software... which btw you could also use C++ for, and it is used here, albeit w/ care). On a one man project it's also much simpler to simply write good modern C++ code than it would be on a large scale project w/ hundreds of programmers. I've also read that Rust's build system (nice as it is) has still limitations w/ very complex build setups...
And whether it's good to use C++ in 2024 for a new project... C++ will be around for DECADES at this point, it has a swath of libraries and tooling, good compilers producing optimized output targeting everything under the sun... yep, it's not part of the "hype around town" languages on Reddit or other boards, but C++ is used every single day in almost every industry down the line by millions of programmers!
What exactly is your worry? That you can't compile your code from 2024 in 3 years? Relax about the online hype... there are areas where EOL languages are still used... C++ isn't dead yet, won't be for a long time. It won't pick up steam any time soon it seems, but for what it can do (including its tooling and libraries) it's hard to beat, and it's not obvious to me that Rust and Zig are obvious "successors".
Zig isn't even at a 1.0 version yet w/ no clear roadmap to get there... I'd be much more worried using it for a serious project than C++... and C++ knowledge will be better on your CV than "Zig knowledge" (which most people won't even have heard of).
There’s gonna be a bit more headache at each step of the process (finding the right libraries, building your code, and learning the language) that might come easily to someone who uses it professionally or used it extensively in college.
That being said, I think learning C/C++ has value in A) the areas you mentioned where it’s used extensively (e.g. kernel, embedded, or HPC dev) and it’s a good lang to know if just to understand how computers work a bit better. This is purely ‘extra credit’ though IMO if you’re already a productive developer.
C++ has a lot of pain points that are being either tackled by the committee or the community. But those pain points still rear their ugly heads.
But majority of the code for HPC and ML is written in C++ or has its core written in C++. Leaving such a huge set of libraries is not an optimal decision if you want to deliver your code without having to yak shave everything.
Between Rust and C++ I tend to pick Rust for better tooling and simpler control over LLVM. It's entirely up to you, but I wouldn't be caught dead running Valgrind on my multithreaded machine learning app.
Zig is a better language than Rust but it is even further behind in native support for the HPC/ML space.
If I were starting a new project today, it would depend on the project and who I was doing it for as to the language I would use, but C++ would definitely be on the list.
For machine learning you have the pytorch C++ API: https://pytorch.org/cppdocs/
You dont have to use every single feature. Use whatever is required and if the need ever comes, go in depth with the language.
Its about to become way more complex and cooler after c++26 and 29 [with possible introduction of contracts and reflection!]. There is no way to completely learn this language anymore. I am not even gonna try.
I like the simplicity of C and not having for wait several minutes to rebuild a project. Have you thought if Python and Cython would be adequate for the task you want to solve?