This line is now drawn as Line Graph. If you change type to Scatterplot (XY) but drawn with line and no markers, you can get crossing vertical axis at 0. This line (both lines) shall be drwan on secondary axis, and you will have to play a bit with axes visibility. First making secondary X visible. The making sure data series for lines include X values. "synchronizing" primary and secondary axes (probably you don't need secondary vertical, which will be swithed on by excel by default).