IT might be possible to make an image of the Z2 HD...then re-image a HD from a Z1. that way the HD from the Z1 would be identical to the Z2. All boot strap material should be the same, or improved for faster booting.

Yes you can, you would also have the updated Z2 on your Z1 hardware. And you would lose your bypass. But yes that would work.

I don't know if the benefit would be in boot up time. What's the time a Z2 takes to boot? Is it really that much faster?

Times differ depending on what the last function was on when the vehicle was shut down (if people want to time for a comparison).

this coocho has just made two completely worthless threads