The necks on the new ZM are "UNFINISHED". That means that it's just bare wood that's been sanded smooth. I personally love the feel of bare wood so much so that I sand finish off all my guitar necks. To clean them I just wipe them down once a week or after sweating a lot during playing one. The oils in your hands will actually treat the wood to protect it, the only problem with that, for some people, is that you get dark stains on the neck after quite some time. I saw an Ibanez Jem with a maple neck that some one used "Simple Green" to clean. I've never had this problem yet. If the neck gets an extremely dry feeling then I use a little 3-in-1 oil or fret board conditioner on a rag. Put it on and wipe all that you can off quickly.
Bottom line is just play it and wipe it down. If you need to use something natural products work the best to clean it.
P.S. This is my SE CU22 that I still need to do some clean up on, but you can get the idea.