Crap, I thought GOG.com had the Infocom collection digitally available, but I seem to be mistaken, they just have a couple of things. Nobody seems to. I bought it a long time ago, when digitally downloading things was a novelty.

Well, if the copyright gods will forgive me, it should be in this collection, which I can find no particularly legal way to purchase in a way that gives money to any rightsholders: http://www.myabandonware.com/game/the-lost-treasures-of-info... I don't know, but it is likely the core z5 files can be found in there with a bit of hunting.

The first Lost Treasures of Infocom is legally available for the iPhone: https://itunes.apple.com/us/app/lost-treasures-of-infocom/id... Though, bizarrely, not for Android.