I recommend trying to put the chair into the car like this:
None of the other ways seemed to work, for example: the trunk and the back door. The legs and the arms and the back... they just don't play nice with the shape of the car doors.
But that configuration there... It doesn't mean the plastic chair has to hang out upside down on the front passenger seat like that... (in fact, the door won't close and the arm rest is obstructing the gear shift ) Once it's inside the car, if you recline the passenger seat and maybe the driver seat, you can twirl the chair around inside the car all you want.
Then maybe you can fit two chairs!
This was a very satisfying project... to not have to return these chairs "because they won't fit in my car" and to get to wrestle them home to my deck where I sat on them in balmy May-Seattle weather until about 10:30pm.