Romulas,

It's not clear where you want to see zstd used.  Here's a trivial 
patch to add Zstd to ‘guix pack’, if that's what you mean.

I didn't submit it in the past because I dread bikeshedding the 
compression level.  -3 is the default, and compresses slightly 
better than gzip in a fraction of the time.

Kind regards,

T G-R