the difference between a ZJ and a CJ is huge. CJ's were produced in the 70's and early 80's and were the precurser for the current wrangler (YJ + TJ). they are now largely modded up for off road use. ZJ's are what you know as Grand Cherokee's. they are the model years from the begining of them being produced till '97 i think. after that they underwent a major remodel and became the WJ's. anymore questions or in depth things just ask.