How do I get my dog and cat to stop fighting?

Thanks to all who took some time to answer my call for help. I was at the end of my rope with this and I am actually trying something that no on suggested through the forum.. One of my coworkers suggested a muzzle for the dog when she retaliates on the cat. The cat cant hurt the dog as he has no claws and doesnt get close enough to bite. So far it has been a couple of hours the dog has worn the muzzle 3 times for about 10 minutes each time and I tell you it is working to get my cat relaxed in the same room and the dog deterred from chasing the cat. Thought someone who may be going through this could use the info. The muzzle was only 10 bucks from Petco and so far a good investment. The dog only has to wear it when she goes after the cat. She will soon ociate this behavior with getting a "not fun" thing wrapped around her nose. Yay!