I don't know how good their tracking is, but zanox network is really huge (it has around 2500 programs) and almost no negative feedback from users on various forums, so I predict they are legit.
I like zanox and i use it. Great statistics (the old one and the ne BETA) and nice rewenue. The coolest thing that the programs hawe many promotional tools so you can chose what you need.
Zanox could be problematic when you ask them for a conversion tracking pixel. It took us over a month to have one placed on their sites
Zanox is good and they pay out. I do not have problems with them and I am very satisfied. The only downside of the zanox codes is that they are full of validation errors.