Lots to say but in a mighty small brochure
Have you got plenty to talk about but it needs to be contained? In other words, your message cannot be communicated in just a few sentences. The way the Z cards fold down allows a really nice story to be told in an interesting format. Z Cards are so dinky that users are more likely to keep the communication piece. Therefore, as marketing material, it tends to have better longevity compared some some brochures and leafets.