Thanks a bunch, Dackel -- very helpful. So all is revealed!
It was confusing for BMW to show that Space Grey coupe in the Limited Edition preview photo because it appears to have options that are not available with the package (Style 261M wheels and M-Sport body kit).
So ZED can't be combined with M-Sport, but it already has the black headliner and a sports steering wheel. It also includes larger and wider wheels and tires (18x8 w/215s front, 18x9 w/245s rear), but no suspension upgrade to take advantage of the extra grip. I'm still hopeful ZED can be combined with the Performance Suspension and Sport Seats to split the difference, because those are the glaring omissions from M-Sport on a 128i.
Interestingly, the ZED package allows the choice of chrome or black window trim, which is cool for those of us who care, and it includes the price of metallic paint (Mineral White, Space Grey or Black Sapphire) and matching floor mats. I'm also hopeful that the combination of ZED and Premium will result in some savings because BMW is otherwise double-dipping for the cost of leather.
Here's the remaining mystery: what is 345 Chrome Line Interior? When the ZED package was announced in December, the interior trim was described as "FineLine Stream wood trim." I sure hope BMW just renamed it or something because Chrome interior trim sounds odd.
The ZED-equipped convertible at the Detroit Auto Show had wood: http://wot.motortrend.com/files/2013...on-cockpit.jpg