You can file both petitions together in one single package. If you go for premium processing (costs extra $1000), both petitions can be adjudicated within 15 calendar days. With regular processing too, it will be lot more time consuming than premium processing, but there is a good likelihood that both petitions are adjudicated at the same time. However, please do not get surprised if H-1B is reviewed first, followed by H-4 in regular processing cases.
Also, you have to file both H-1B and H-4 petitions simultaneously. Many people in the past have suffered not knowing the simple fact that when H-1B extension is being applied, H-4 should also be applied. This is a famous problem and you will find it in many forums.