I recently recovered a zip archive with some files I need access to, but I can't remember the password. All I can remember is that the password was short (around 3-4 characters), and contained only lowercase characters and possibly numbers). However there is no Incremental mode for this particular situation in John the Ripper. The closest there is is lanman, which also increases the set of possible passwords dramatically by including uppercase chars, which I'm positive the password includes none of.
Although I can edit the john.conf file so that a specific mode goes only to 4 characters, for instance, I don't know how to customize the set of characters to try. How could I do this?