Where are crumple zones located in a car?

Mainly the front and back. The part where the people sit is stronger. Front and rear body panels are designed to fold (or crumple) in a certain way. Plastic bumpers are the first to give but this has little effect in slowing down any impact. Next, the chassis legs and inner wings and outer wings are designed to fold progressively to slow the impact down, even the air in the tyres can help here, acting like a cushion. Engines and gearboxes on the subframe should go downward as well, and the steering column is collapsible (like a telescope).