Yes, you can use them both at the same time, but honestly, it might be a bit overkill, and the skin can only absorb so much.
Actually, the other products on the website has some stacking abilities. You can stack Xplosive Burn, Lean Fast, and Carb Free together or Cardio Heat with Lean Fast and Carb Free. A woman I know was taking Xplosive Burn, Lean Fast, Carb Free, and TargeX Burn and she said that it felt like she was living in a hot house.