Zero air speed or zero ground speed autos are no problem if you practise, just like any other tricky manoevre. Basically if you start at a steady 40 kts into a 20 kt wind & run on at 20 kts, you would be surprised how easy it is to gradually reduce your airspeed to achieve zero ground speed. You also should start with a light machine & slowly build up weight. Of all the dozens of pilots I've trained to do this, not one has had a problem, in fact they had more problems judging when to flare & level off.