Larger pages will yield higher compression ratios, as will zstd (slightly slower than lz4).
Mileage varies, but on some of my databases, between the 64KB pages (zfs recordsize) and zstd, my compression ratios approximately doubled, from about 1.8:1 to a little under 4:1. This will all heavily depend on the type of data you are storing, though.
zstd has adjustable compression, so if you have tons of CPU to spare, you could turn it up from the default of 3 (probably optimal cost/size compromise) to high teens for a compression boost.