Welcome olivichel! It's great to have you here, please make yourself at home. We actually got our original copy of ZT there so long ago, as well.
There are some things to know about adding items into your game, such as to be sure to put them in the dlupdates folder. Also, if you add more than about 295 files, your game could crash. There is also a 'crack' file that allows you to boot the game without using your discs, which could keep them working longer. I'm attaching it here. If you decide to use it, simply remove your zoo.exe file and save it somewhere, then replace with the attached file.
Again, welcome.
zoo.exe