Z specifications prepared using troff mark-up are typeset via cadiz - troff is not run directly by the user, but indirectly by cadiz. The formal paragraphs are prettyprinted by cadiz, producing consistent layout to which readers can become accustomed, but over which the author has little control.
Printing is a three stage process:
For example,
cadiz -P filename.z grops filename.dit >filename.ps lp filename.ps
This illustrates translation to PostScript using the grops tool, and sending to the printer using the lp spooling command. That is what's appropriate for my printer; you may have to work out an alternative.