>! The idea here is to force black to move his knight. We can see that the king is already in a state of not being able to move because of the white king and light squared bishop. And we can see that the dark squared bishop on any of these highlighted squares would be mate. 
>! [![enter image description here][1]][1]

>! So all we have to do is bring the dark squared bishop to f2 and so forces the knight to move. The knight cannot simultaneously block or defend knight b6 or h4 at the same time nor can it take the bishop.
>! [![enter image description here][2]][2]


  [1]: https://i.sstatic.net/OH8K9S18.jpg
  [2]: https://i.sstatic.net/OhnnHd18.jpg