The command ‘-znew.sty’ changes the default style-file name fweb.sty to new.sty. The command ‘-z’ (with no argument) means “Don’t read any style file.”
Normally the style file is read from the same directory in which the
web source file resides (or from the path defined by the
environment variable FWEB_STYLE_DIR). To force fweb.sty
to be read from the current directory, say ‘-z.’.