I was a bit hesitant on zstd before since there is no pure rust library for it, meaning we need to link another c library, but Roblox already using it in various places is a good argument for Lune also having it. I think the benefits outweigh the costs here.

This should be very straightforward to add, just enabling the zstd feature in async-compression and adding a new match branch, so if any new contributor wants to pick this up as a first issue feel free :)

I support this, another usecase here that wasn't mentioned by the OP was that Roblox sometimes compresses rbxm files uses zstd, the exact conditions for when it does this are a little hazy, but every signed model is compressed using zstd over lz4