Sorry to hear about your experiences, OP
FWIW, Z1 messes up something on pretty much every order I place. It's never been major and has always been resolved satisfactorily for me, but still it seems like there is always some hassle to deal with when I use them. But I can't say I've had a lot of issues with their products. Other than a few cylinder failures (thank goodness no need to drop the transmission again), the Z1 CSCEK has been OK since I installed it several years back.
Another problem I've found is it can sometimes be hard to speak to the right person. They usually tell me who I
need to speak with, but I generally have trouble getting a hold of that person and have to send an email asking for a return phone call (and usually have to wait a few days).
More and more of my orders are being placed through ZSpeed these days. Joe has the best customer service out there.