I have saved data into db using CoreData. I need to fetch data from my table in same order that it was saved. Inside table it is ordered by Z_PK - hidded CoreData key. How can I create such sort descriptor. If I use fetch request without sort descriptors my data objects have wrong order.
Anything not exposed to you by the Core Data framework is an implementation detail. The fact that Z_PK exists, and currently suits your purposes, cannot be relied upon.
If creation/save order is important to your model, then it should be included in your model. There's really nothing else to it.