Here is a screen shot of MaxZip (GIF image, 10K).
It is running Graham Nelson's excellent text game Curses!
(also freeware, but not distributed by me.) Note the scroll bar,
full-justified text, boldface, and full mouse and keyboard text editing.
Color is also supported, although not visible in this screen shot.
The interface is a Mac interface. No surprises. (Well, maybe a couple.) The documentation is all available on-line, under the Help (Balloon) menu. The important feature is that MaxZip can build a stand-alone Macintosh executable from a Z-code file. (And the stand-alone program can unbuild itself into the Z-code file and the original MaxZip.)
Note that this is explicitly intended to be used by game authors to distribute Mac versions of their games. To this end, I declare that any stand-alone game that you make from your own Z-code file is entirely yours; you may give it away, sell it, or do anything else you like. The only restriction is that you may not interfere with the user's right or ability to build the original, freeware MaxZip (which will not contain your Z-code.)
The Z-code engine in MaxZip is taken from ZIP V2.0.7 by Mark Howell (howell_ma@movies.enet.dec.com).
You can download the Mac executable. It's a BinHexed file, about 193K. The source is available separately; if you feel like hacking around with it, you can download the source code (225K.) But if you only want to play games, you just want the executable.
If you like the MaxZip interface, you may also be interested in XZip, a similar interpreter I wrote for X Windows on any Unix machine (including Linux). There's also MaxTADS, an interpreter for playing TADS game files on the Macintosh.
Here is the directory of Z-code games in the IF Archive.
I myself have written several games in Z-code format. People seem to think that some of them are pretty good.