To the user with issue with frotz.
Frotz is one of the only ones that you can't open directly the game files.
tads, glulxe etc you can just hit enter with the extention of the file you want.
Frotz you need to open frotz, then open the dat or z file you want to open.
If you open the z file the addon will not run, its never been explained.
I do the same with agility though you can open agx files ok with the addon and it works.