you need radio keys, or a coupld of bent knitting needles, insert a pointinot each hold, push the pints towards the doors, so the points in the holes lever towards the unit, then pull back, you'll see that there are 4 clips about 6 mm, inside the holes,
the pins are like £5 from Halfrauds or £1.80 from a garage/car modifying place/audio shop. or sed nitting needles/nails/coat hanger- potentiallly free.
not to say jays method is not simple but could crack the units lip or the heater controls.