If a pony turns into an undead with no ‘soul’ ( aka no comunication is available, the host of their body is gone )

Would their cutiemark disappear since the cutiemakr is magical and connected to the ponys special talent? or would it change into its new 'talent’ or maybe turn into something that isnt really a mark ?

Lico is a zombie, but she still have her soul left, and thus having her cutiemark still. But what would happen to a zombie-zombie thats only after brains?