A Wazir in a Billiard Room

h=3

Bouncing Bishop* in g3

Wazir** King in g4
No White King

1. BBb8, a6 2. WKg3, a7 3. WKg2, axb8=BB = ***

* A Bouncing Bishop can bounce off from all sides of the chessboard.

** A Wazir is a fairy chess piece that moves like a Rook, but can go only one square.

*** I could not verify my solution.