The present midi editor zooming with mousewheel is inconsistent with itself leading to some annoying behavior when zooming.
If you zoom anywhere where the viewport would not pass the left of the midi item you are editing it behaves as expected. The zoom centers around the mouse cursor.
However, if you would zoom to expose anything beyond the left of the current item, the viewport snaps to the left of the item, so you are no longer zooming on the mouse cursor.
It would be more consistent if we always zoomed toward the mouse cursor.
See me struggle to zoom centered on these left notes: