The default should be single zone. Dual zone should only be active if you've got another screen hooked up to it. A little more detail about what exactly the problem is would be helpful. Are you saying you only get video on the additional screen(s) and not on the indash itself? If that's the case then it's a safety feature and you have to have the parking break on or have grounded the parking break wire.
I cannot get sound from a cd or dvd in the single zone. Only the dual zone. I get the tuner in single zone but no cd/dvd. I can get the picture on the in-dash. I cannot figure it out.