There's a nice comparison of compression algorithms (including zlib, zstd, brotli, snappy, etc) here: https://quixdb.github.io/squash-benchmark/
It's nice because it uses many datasets and machine platforms.
Unfortunately the graphs leave a bit to be desired, especially when you're trying to compare two algorithms. They provide the raw data, but it needs a little munging to make it workable.
For my day job I made the following graph to compare zlib level1 and zstd. This was using the "peltast" platform which is a Xeon based system, because that was most relevant for us.
I'll make one with brotli now.