Welcome and sorry to hear about your problem. By "double downshifting", I assume you missed TWO gears as you attempted to shift down? If it was a fifth to third misshift, and you hit first gear instead, you might have a BIG over-rev. It also depends on how close to redline you were when the mis-shift occurred. Did you note how far your VQ revved to?
One of the biggest problems with a big over-rev is a bent valve, or other valvetrain damage. That's something the Z's diagnostic system, or even a compression check may not detect. I doubt sensors or injectors would cause a multiple misfire, but continued misfires under load are not good for a precision built engine like the VQ.