An RBZ file is a plugin file used by the modeling program, Trimble SketchUp, for computer-aided design (CAD). It is a compressed ZIP file that contains one or more Ruby scripts (.rb files) inside it. That is why the file type is RBZ (RB + Z). RBZ files are easy to distribute and isntall over the network due to their small file size as result of compression.
RBZ File Format - More Information
RBZ files are compressed ZIP files that contain a Ruby script file. It is compressed with the most commonly used compression method DEFLATE, which is described in IETF RFC 1951.
How to open an RBZ file?
You can open RBZ files with Trimble SketchUp on Windows as well as macOS.
In addition to these, since RBZ files are compressed ZIP files, you can extract these with standard ZIP extraction utilies by renaming its extension from .rbz to .zip.
SketchUp is a 3D modeling software widely used for architectural design, interior design, film and video game design, and other related fields. It was originally developed by @Last Software, which was later acquired by Google in 2006. Google continued to develop and improve SketchUp before selling it to Trimble Inc. in 2012.