Aaw, that really sux!! When I got my Z over 4 years ago, I'd only had it for 1.5 weeks, and some little delight keyed it, happened quite a few times since.
The trick I've found is careful use of swirl remover, leave it to cure (as per directions whatever brand you are using), then do another layer, same again. Then once all done, put a couple of layers of wax over, obviously letting each layer cure properly, using good microfibre cloths. This process has hidden all bar the worst key mark (very deep). Won't do a respray until it's not a DD anymore.
Also used this process on a number of black beasties I've groomed, worked really well.
Have a bash at that anyway, let us know how you get on.