I looked at the Marzocchi kit for my Z1s as have converted from air to coil. In the end I was feeling fancy so went with smashpot and a couple of springs to work out whats best as I am very much on the medium/firm boundary.
One slightly related but maybe not that related question – Marzocchi state that the 29″ Z1 can only go to 170mm. What would happen if you bumped that up to 180mm? The smashpot kit would go up to 180mm. Would the fork explode? The 27,5″ Z1 does go up to 180mm. I know different forks etc but……what would happen?*
*This is not considering frames or their suitability for 180mm forks.