Problem
These two muscles have an effect on the skeleton in common. Most of these muscles also do other things, but you are only interested in the common action. First describe the common action, using the correct terms. Then find out what the origins and insertions of the muscles are and figure out how the two complement each other in performing the particular movement you have identified that they accomplish in common. In other words, how do their motion and relative effect differ? Finally, try to explain why you need both of them. Do not concern yourself about other things that either of the muscles do, just those that affect the common action.
Muscles - Gluteus medius/tensor fascia latae.