You're 2/3 correct:

x - extract

z - gzip format

f - file (must be last so it parses the filename arg correctly

I also add "vv" in the middle so it lists every file as it goes, so I can see it work instead of just waiting with no output.

It's not often I actually unzip stuff on the command line these days, but saying "extract ze files" in a terrible French accent in my head when I do is a highlight.