Only if you have uncontrollable cholesterol with either medication alone and you are closely monitored by your doctor, can you take both. You should have also probably have tried and failed (meaning your cholesterol was still too high) a combination statin and zetia.
The risk of taking a statin (lipitor) and a fibrate (tricor) involves your liver and muscles. They both can have a negative impact on these organs, and when taken together, they increase your risk of having negative effects. Watch out for muscle aches, and your chance of a serious side effect called rhabdomyolysis is almost ten times higher. Note that on the combination, this is still rare, happening in only 5 in 10000 people.
You doctor will likely draw blood labs on your to monitor your liver and CPK (a muscle enzyme) to make sure you are responding well to your medications.
To your health,