If it were me, this just kicked into the "bullshit" level. Or, to quote that old comment: "What we have here is a failure to communicate".
My immediate reaction is your dealer has pushed this to the back of the shop and doesn't want to deal with it, but that's just my gut feeling on it. In any case, I can't imagine that Zero, at the corporate level, would want this kind of lack of customer service to go unaddressed.
I've dealt with a few instances of this kind of thing before, and actually been thanked by the companies involved. Here's how I approached it.
First, in your communication, remember my Dad's advice: Always write an angry letter so that they have to read it twice, or maybe three times, before they really understand how pissed off you are.
Second, write actual letters, on paper. Send them via a service that requires a signature - Express Mail or FedEx works fine, but Certified Mail is good too.
Write the letter to the highest-up Zero guy you can find the name of. I believe there is a VP of Customer Service who was just anointed to the post a few months ago, but I'd have to check. CC the owner of the shop at your local dealer - if it's a small shop, that's easy, if it's a bigger company that owns a bunch of local shops like we have here in Boston, it's harder to get a name. And finally, and most important, CC your state's Attorney General's Dept of Consumer Affairs, and if necessary, open a case. If you have a friend who's an attorney, CC them too. No comments necessary in the text, just show the CCs at the bottom of the letter.
Feel free to PM me for coaching on this if you have questions. I'd even write the letter for you, it's good anger management therapy.
The letter needs to state, clearly and professionally, when you bought the bike, the steps you've taken to get it fixed, the communications you've had, the degree to which you're displeased, the remedies you'd consider acceptable, and the steps you'll take if the situation is not addressed. I'd consult your state's "Lemon Law" if you have one, too. Imagine yourself not you, but your lawyer writing this for you. It helps manage the tone.
The first time I did this it was purely to get the whole thing off my chest. I just was so pissed off I had to do something, and get someone's attention, for some stuff that the dealer did that was just off-the-hook BS. I got a phone call from the VP of the company whose product it was - the guy I cc'd. They replaced the product, and refunded the purchase price too. (This was a $2k product) And this was before the internet.
It took me about an hour to write the letter, find the addresses and copy and mail it.
You may have a dealer who's slacking, you may have a sticky issue, you may have service techs at Zero who are slacking, but I'm pretty certain that if the VPs find out about it, and that you're talking about it online, they're going to fix it.
(edit: I remember now what the manufacturer's VP told me on the phone. "I really appreciate you bringing this to my attention. Whenever we talk to our dealers, or visit them, they never tell us about this stuff. Everything always sounds perfect."
I'm pretty sure the comment about "unicorns and rainbows" that I recall may be my own memory's embellishment.
)