Ambulance is a feature length chase scene, where in the back of the car a doctor is doing a surgery on a person. In 6 Undergound the first scene is 20 or something minute long chase scene where in the back of the car a doctor is doing a surgery. In 6 Underground the doctor is played by Adria Arjona and in Ambulance the doctor is played by Eiza Gonzalez which is interesting and perhaps was intentional. Since both actresses look so much alike that a lot of people confuse the two. Michael Bay is self-referencing here again.
In a nutshell, the movie feels like a mash between Adrian Lyne's Flashdance, Damien Chazelle's Babylon, Ti West's MaXXXine and Lars Von Trier's Nymphomaniac, well stirred and served in a colorful presentation straight from Nicolas Winding Refn.