> the whole range from gzip -1 to gzip -9

gzip compression levels are almost useless and typically result in very little actual compression ratio differences, but typically with massive CPU usage differences.

zstd doesn't do everything better than gzip though; I believe gzip still offers somewhat faster compression for equal compression ratios last time I looked (but decompression is much faster). I mostly replaced gzip with zstd myself, but there are still scenarios where gzip might be preferable.