When you take two steps on a fast break layup you are actually establishing a pivot foot then taking one step (it is really the same rule).
Is this legal? Jump from pivot foot, then jump from the other foot. (yes, but nobody does it because it looks wrong). rule: is not traveling til you put the pivot foot back down. This is actually the eurostep when done when picking up the ball while driving to the basket. Same travel rules apply whether picking up the ball off of a dribble or setting a pivot foot before.