Get a set of the u-shaped DIN radio removal tools. You can do the job with coat hangers but the right tool makes it easier.
You need to seat the tools and wiggle them a bit, then grab the radio via the cassette opening and it should pull straight out with a little tugging.
Bought those identical tools today and still no luck. I hear the clicks and jiggled the hell out of the radio and still it won't budge. Could something else be preventing it from releasing?? It's the same OEM radio shown in this thread.