A while ago I had the chance to briefly check out the Zero parts-ordering software (just looking over someone's shoulder, not actually using it). It's similar to mainstream software I've used online, but not identical - and at least one difference can significantly affect ordering (see below). The parts program is run over the Web, probably from Zero HQ.
As I recall, there's a main drop-down menu set that shows the various Zero models and years. The user specifies a year and model, orders parts for it, then changes to a different year and/or model to order parts for that one. The fleet models (DSP, MMX, etc.) were completely absent from the software I looked at - I have no idea how parts are ordered for those (no '16 MMX front & rear wheels for me - oh well).
Once the model & year are selected, there are various diagrams that can be opened. Unlike other parts programs I've used, there's no parts list underneath corresponding to the diagram numbers; instead, the user clicks on a number in the diagram, and a new window opens with specific part information. This extra complexity might be warranted if there were lines and lines of info for every part, but all I saw were single lines with part number, brief description, and possibly price, with the rest of the page blank. All this info - including superceding P/N's - is included on other ordering programs' parts lists, under the diagrams.
One thing you do NOT want to see in the part screen is 'Part Not Available' (which I now believe actually means 'Part Availability not available').
In the ten orders I've made so far. this has happened in at least 7 of them, sometimes multiple times per order; in each case I re-ordered the parts in the next order, and have gotten every one so far. After seeing the software in action, I think there may be a half-assed workaround for this situation if the part you want is used over several models and/or years; you can order the same part for multiple years/models, and chances are one of them will show as available and can actually be ordered - or you can re-order as mentioned above. Since all this parts stuff is dealer-eyes-only it's pretty difficult to determine for certain which parts are used for which years - I guess the Zero site photos will have to suffice, at least for now.
A side note regarding the chain kit - all the individual parts can be ordered from the '13 MX section, along with the shock protector.
As mentioned in the recent 'Dealer Thread', the standard parts-ordering model is to have the parts sent to the dealer, where they can be picked up or re-shipped to the customer. Honestly, for the present I think this arrangement is probably best; I've had problems with a number of my orders, and it's far easier to let the dealer handle those. I'm sure in the future Zero will farm out the parts thing to third-party Web entities like everyone else, and we'll be able to order direct online.
Ray