Change in Height as a function of change in BF.
These figures are correct even if rebalancing has occurred.
Cases marked "--" are impossible.

Figures are given for insertion/deletion from left and
right sub-trees separately, and a combined figure for
where it's unknown which sub-tree was modified.

         InsL  InsR   Insert  |  DelL  DelR   Delete
 E->E      0     0       0    |    0     0       0
 E->N     --    --      --    |   --    --      --
 E->Z     +1    +1      +1    |   --    --      --
 E->P     --    --      --    |   --    --      --
 N->E     --    --      --    |   --    --      --
 N->N      0     0       0    |    0     0       0
 N->Z      0     0       0    |   -1    -1      -1
 N->P     --    --      --    |    0    --       0
 Z->E     --    --      --    |   -1    -1      -1
 Z->N     --    +1      +1    |    0    --       0
 Z->Z      0     0       0    |    0     0       0
 Z->P     +1    --      +1    |   --     0       0
 P->E     --    --      --    |   --    --      --
 P->N     --    --      --    |   --     0       0
 P->Z      0     0       0    |   -1    -1      -1
 P->P      0     0       0    |    0     0       0