There is no defined standard for metadatas in cbz. There are different implementations.
For ACBF I found that:
http://acbf.wikia.com/wiki/ACBF_Specifications
Fçr ComicRack you have an example here(xml stored as a file named ComicInfo.xml) :
https://wiki.mobileread.com/wiki/ComicRack
And for ComicBookInfo (json stored as a zip comment there):
https://code.google.com/p/comicbookinfo/wiki/Example
I'm not sure what metadatas Calibre is able to read from cbz archives, but I'm pretty sure there are plugins for that thought.