Online Community of Zenith Builders and Flyers
There are quite a few positive reviews in the backcountrypilot.org forum. One guy (I think courierguy) has over 1,000 hours on it.
We seriously considered it for our Cruzer, but did in the end not feel comfortable about buying a new Rotax only to void its warranty by installing a Zipper kit.
Thanks Oliver, that's a great website.
One of the challenges I see is a low to mid time 80 hp 912 at a reasonable enough price to make the zipper kit cost effective is nigh on impossible to find. The few that do pop up have had prop strikes, or are older and need a lot of expensive updates and inspections, often times both. When a low to mid time used engine with complete logs and all the updates does appear, the asking price is usually so high it makes a new engine the better choice.