When you download Zero Install for the first time you get a so called Bootstrap EXE.

This is a stripped down version of Zero Install that uses the feed format to download and run a full version of Zero Install.

If you wish to install Zero Install in an unattended/automated fashion (e.g. in a corporate environment) you can call zero-install.exe /silent

Default settings can be integrated in the Bootstrap process via zero-install.exe.config.

See also: Blog post about Bootstrapper