Okay, here's the deal on that Zombie Wars demo.
Gee Whiz! Entertainment released a demo based on a beta version of Zombie Wars, called the "Zombie Wars Internet Demo" (zwdemo1.zip). It was a Win16 game that required WinG, but was clearly a DOS game (probably based on the Alien Carnage engine) that had been ported to Win16. From Gee Whiz! Entertainment's website:
Requirements: 486-dx66, Win 3.1, 8 Meg ram, 8 Meg HD space, Colour monitor.
Recommended: Pentium, soundcard, 16 Meg ram, 8 Megs HD space, Win95, Colour monitor, Joystick or Gravis gamepad.
NOTE- Windows 3.1 version requires the WinG library.
According to the readme file, the demo is from 29 July 1996, but someone packed it into a Win9x installer on 10 July 1998 (the file you linked to). Since the original demo was based on a beta version of the game that Gee Whiz! probably had no interest in distributing any more, and the copyright notice wasn't updated to "1996-1998", and the installer calls the game "Halloween Harry 2 - Zombie Wars", it looks like this installer was created by an anonymous third party! But since I can't find the original zwdemo1.zip, I'll put it on the site anyway while I contact John Passfield about it.
Once the game was done, it looks like it required Windows 95. Gee Whiz! created downloads of the complete game (split into two zip files, plus two optional movie packs), that would only let you play a (different) special demo level until you unlock the rest by registering the game.
Files:
zwgame1.zip (4,297,152 bytes)
[Have]
zwgame2.zip (4,707,765 bytes)
zwavi1.zip (6,261,359 bytes)
zwavi2.zip (4,350,169 bytes)
The registration price was $24.95. By November 1998, Gee Whiz! reduced the registration price to $9.95 and linked to a company called RegNow that handled registration for shareware authors. According to Gee Whiz's website, the download that accompanied registration was 8,106,539 bytes. (Perhaps zwgame1.zip and zwgame2.zip were combined into a single file, but you still had to download the movie packs separately?)
From the Gee Whiz! website:
Requirements: 486-dx66, Win95, 8 Meg ram, 52 Megs HD space, Colour monitor.
Recommended: Pentium, soundcard, 16 Meg ram, 52 Megs HD space, Win95, Colour monitor, Joystick or Gravis gamepad.