The Short Crooked/Straight Bishop
It's hard to find good colorbound substitutes for the Bishop. The FD, FA, and DA are too weak, and the FAD is too strong; the DAmF is too hard to get used to.
zF2
The zF2 is a crooked Bishop that can only go two squares. It goes to the same squares that the FD would go to, but can be blocked: from e4 it can go to d5, f5, e6 (and other squares), but in order to get to e6 it must go through either f5 or d5.If the zF2 starts the game on f1, it cannot jump to f3 but must wait for one of the Pawns (e2, g2) to move. In comparison, an FD on f1 can leap to f3 no matter what.
Obviously, the zF2 is weaker than the FD, and the FD is known to be weaker than the Bishop.
F2
The F2 is a Bishop that can only go two squares. It is weaker than the FA which is weaker than the Bishop.
F2zF2
The F2zF2 combines those two pieces. It is weaker than the FAD, and the FAD is stronger than the Bishop. Perhaps the F2zF2 is just right?