The most obvious difference is that you've got one big game, with one big map, instead of 3 smaller ones. Also, a few things were added to Zork I, a few more to Zork II, and a lot of new material to Zork III. In particular, don't look for the "Oddly Angled" puzzle in the original mainframe Zork.
You can find a mainframe Zork map at https://wildfireds.files.wordpress.com/2010/11/dungeon.jpg (link current as of November 14, 2015); DOS and Linux ports of the game can be found all over the Web, by a simple Google search, and somebody has apparently even ported the game to run on any standard Infocom game parser.
Some of the differences can be quite frustrating. Some of these involve different objects (or at least, objects that look different), while others involve limitations in the early parser's ability to understand English. This ain't the "Plundered Hearts" parser!
Monday, April 4, 2005. Links updated 11/14/2015.
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