How to return to XY and Z zero points

The dot in the center of the xy± will return to xy zero and the do in between the z± will return to Z zero.
When you do this we would suggest doing Z first to get your bit clear of your material height. (or at least validate that its above the work surface) if you hit the double circles and its below the work surface it will only do X & Y and likely break your bit. If you do Z first it will clear the height issue then you can hit the X,Y Zero.