Are you leaving from Zagreb and connecting at CDG? If yes, then you should have your luggage checked through to your final destination and get your boarding pass in Zagreb. If you can do that, it would give you more time in the city, you'd need to allow for security, boarding and the return metro/train to the airport.
However, I think a couple of hours in Paris would make you wish that you had more time, so I agree with Jack, consider doing breakaway and spend two or three days in Paris. The hotel he recommends looks good and it's a good location, near Ile de Cite, and one of my favorites, plus it's near the Seine, great for walks. There are many, good, small, reasonably priced hotels in Paris, but consider the location when you book. It's nice to walk out the door and be within walking distance of some of the finer aspects of the city.
Have a wonderful rtrip.