I have seen a couple Zico offspring, and talked to the owners of others. I also own his sister Zara.
What I have seen/heard is that he produces tons of drive, good grips, and hard hitting dogs. They do have a tendency to be sharp. I've been told a lot of the dogs in Zico's litter are not social (Zara is) so the sharpness wouldn't surprise me. Structure in the offspring is OK. I don't think I'd take a female with poor structure to him though.