Fritzing software supports export to several graphics formats, including JPEG format. It is possible to create raster image of the content and you can access this function under the File ► Export menu in Fritzing.
The preferred output option is to vector graphics formats, because the content is usually vector based. It is unlikely any other tool can be used to with .fzz files anyway, so using the original software is your only option for fzz to jpeg conversion.
Updated: May 15, 2023