you don't have to be a rocket scientist (to do something)
You don't have to be particularly intelligent to be able to do or understand something. You don't have to be a rocket scientist to learn how to change the oil in your car. You don't have to be a rocket scientist to know that you have to unplug electrical equipment before you try to fix it.
you don’t have to be a ˈrocket scientist (to do something)
, it doesn’t take a ˈrocket scientist (to do something)
used to emphasize that something is easy to understand: Of course this model sells more than the others — it’s the cheapest! It doesn’t take a rocket scientist to work that one out.