If you have just received an .fzz file and need to view it immediately, follow this guide using the OpenFZZ Toolkit (free method):
In the context of electronics and DIY hardware, an refers to a tool used to open and interact with Fritzing Shareable Project files (.fzz) . These files are compressed archives containing all the metadata, circuit diagrams (breadboard, schematic, and PCB views), and custom part data for an electronics project. fzz viewer