Vita has a series of VM porcelains
VM 13 ..... metal ceramics ... Vita Master NP and other alloys
VM 9 .... zirconia
VM11 .... Vita Suprinty and works with Celtra
Newest Vita porcelain for zirconia, Vita Lumex AC
Personally never liked VM 13 but all Vita porcelains come in 3D shades. If your looking for a new zir porcelain I would order Lumex AC hands down.
I'm pretty sure Lumex is compatible with emax but not 100% positive. Being able to easily match 3D shades is a must, and especially on layered ceramics for your anterior cases. Vita's 3D guide and 3D Linearshade guide is being used more by dentist on anterior cases.