yup, zstd is better. Overall use zstd for pretty much anything that can benefit from a general purpose compression. It's a beyond excellent library, tool, and an algorithm (set of).
Brotli w/o a custom dictionary is a weird choice to begin with.
Brotli compresses my files way better, but it's doing it way slower. Anyway, universal statement "zstd is better" is not valid.
This bizzare move has all the hallmarks of embrace-extend-extinguish rather than technical excellence
Brotli makes a bit of sense considering this is a static asset; it compresses somewhat more than zstd. This is why brotli is pretty ubiquitous for precompressed static assets on the Web.
That said, I personally prefer zstd as well, it's been a great general use lib.