Refer to figure.
Shortest distance means that the aircraft follows a Great Circle track.
Because of the meridians’ convergency, the great circles have a changing track direction along their length.

A simple diagram would help to identify the final true track at Z point:

• At the North hemisphere the meridians converge inwards.
• The initial true track is a little eastwards (122^o).
• The Great circle true track is always the clockwise angle from the true meridian to the track direction.
• It is obvious that the track cuts the meridian at Z point at a higher angle, by the convergency 20^o.

Convergency is the change of the true track between two points.

Since the initial track is 122^o, the convergency is 20^o and the track cuts the meridian at a higher angle at Z point, then the final true track is: 122^o + 20^o = 142^o.