The use of a rigorous development environment is needed when developing a complex system, such as real-time and critical systems. Preventing industry from embracing formal method techniques is the lack of industrial strength tools to support formalization and analysis. We are developing an approach and a tool environment for the development of complex systems that integrates a graphical object-oriented technique (Fusion) and a formal method (Z) with analysis tools. The tool, called FuZE (Fusion/Z Environment), has been used successfully to specify and analyze non-trivial systems. This paper describes the specification transformation rules and the extension of the environment to include transformation of design documents such as Object Interaction Graphs.