Has no relation to Disney and has a demonic fox with red glowing eyes. Can't remember the exact name or creator.
Try going to Google search engine and just typing in some keywords like zootopia fanfic demon fox, or something like that. If it's there it will most likely be on a site like furaffinity, aryion.com, deviantart, e621.net. Check out this sites. Sorry if this doesn't help much.