There is a link in the ZedBoard Community Projects to the Silica Yocto Linux for ZedBoard.
Silica has provided a complete package for creating a Yocto Linux distribution for reference boards supported under their ArchiTech program. ZedBoard is one of these. The package includes a complete development environment as a VirtualBox image, and a Quickstart guide with download, set-up and build instructions. The Yocto Project, for which Silica is an official contributor, describes a framework for creating standardized Linux distributions.