zlib-rs => crate replacing non-rust zlib
firefox => where the replacement is happening
trifecta => the foundation sponsored to develop the replacements

Maybe I'm influenced by the fact that I pre-knew all of the above. But as I wrote, it's quite ironic choosing this perfect title in particular to complain about 😉.

On the topic of low(ish) level dependencies getting incrementally replaced with Rust rewrites, a Google employee did a presentation on the same topic recently.