Hi,
To maintain Change Document for custom field:
1. Check if "Change document" checkbox is set in data element.
2. Find Change Document Object for transaction.
You can use SQL trace - ST05.
Look there for line with table CDHDR and statement insert values
(for example for transaction KA02 Change Document Object is KSTAR)
3. Regenerate update program for this Change Document Object in transaction SCDO
Change documents for z-fields schould be generated.
I am not sure about change pointers but they are configured somehow in BD61 and BD50.