Compression ratio largely depends on the cluster size used. For large cluster sizes (16K and higher), typical compression ratios are only 1-2% less than those achieved with the gzip(1) utlity. However, it should be kept in mind that larger cluster sizes lead to higher overhead in the geom_uzip(4) class, as the class has to decompress the whole cluster even if only several bytes from that cluster have to be read.
The mkuzip inserts tiny shell script at the beginning of the generated image, which makes it possible to "run" the image just like any other shell script. This script tries to load geom_uzip(4) class if it is not loaded, configure image as an md(4) disk device using mdconfig(8) utility, and automatically mount it using mount_cd9660(8) utility to the mount point provided as a first argument.
gzip(1), zlib(3), geom(4), geom_uzip(4), md(4), mdconfig(8), mount_cd9660(8)