It appears that .pkz and .pkt files are both used by Packet Tracer software from Cisco, however, a conversion or transformation of data seems not likely. At best you can import and work with the .pkz files in the program, run some simulation and export .pkt file, but that's about it.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.