Is there a general way for zooming in/out on a wx.Panel (all its content should be zoomed as well) ?
Is it possible to define a new sizer type that would provide this feature ?
No. The wx.Panel does not support this feature out of the box. The FloatCanvas widget does support panning and zooming though. You could use that widget instead. Of course, I think you will have to draw the items on it instead of using regular widgets.
Zoom in/out on a wx.Panel