Running zstd it in a tmpfs doesn’t speed up things, at least not with compression level 9.
Right not, I am running out of ideas, I will take a deeper look into ldd, but as far as I know, this may be a rabbit hole, with libraries loading other libraries. strace may be my next attempt so see what actually gets loaded when running the binary.
In theory, a static binary could rule out some possible reasons, I will need to research how to create this (may need to recompile every dependency, which sounds like a lot of work, unless there is a tool doing this automatically).