Jamieson, Fausset and Brown on Zechariah 11:2

2. fir tree ... cedar--if even the cedars (the highest in the state) are not spared, how much less the fir trees (the lowest)!

forest of ... vintage--As the vines are stripped of their grapes in the vintage (compare Joe 3:13), so the forest of Lebanon "is come down," stripped of all its beauty. Rather, "the fortified" or "inaccessible forest" [Maurer]; that is, Jerusalem dense with houses as a thick forest is with trees, and "fortified" with a wall around. Compare Mi 3:12, where its desolate state is described as a forest.