Consider the user generated content to be the content which do not exists before your start your project in Zbrush.
It includes :
- Alpha and Textures or References you like to basically backup within the project Workspace sub directories.
- ZProject (*.ZPR)
- Ztools (*.ZTL)
- Brushes (*.ZBP)
- Materials (*.ZMT)
- Textures Passes Sets you get when you run the Batch Rendering Process (PSD, PNG, JPG or TIFF).
- Snapshots which are kind of advanced brushes that can be saved and loaded from a Slider Slot ( *.ALP, *.PSD).
- Iterative Tileable Masks which are intended to only be reuse in Zbrush workflow. Particularly with a mask based sculpting and texturing workflow.
- Single Pass Document ( Photoshop Only )
- Single Mask Document ( Photoshop Only )
- Layered Document ( Photoshop Only )