In the effort to expand and vary the Symmetrical Chess Collection, the introduction of more sliders became desirable in 2001. Although all of the familiar symmetrical sliders were already in use (i.e., the Bishop, Rook, Queen), 4 additional, new asymmetrical sliders were introduced that exhibit 4 directions of movement. Having an orthogonal and a diagonal component, they may be classified as all 4 possible hybrids between a Bishop and a Rook. So-named Zig-Zag, Zag-Zig, Zag-Zag, Zig-Zig, they are sometimes referred to as the class of "ZZ pieces". These pieces are currently used as the basis for several 2-D games.
The Zag-Zig is a hybrid piece which can move vertically or along the NW-SE diagonal as far as it has a clear path. It ends its move by occupying an empty space or by capturing an enemy piece. Orthogonal movement (only in the vertical direction) passes through rows of spaces that are connected to their neighbors in the row by shared sides. Diagonal movement (only in the NW-SE direction) passes through the corners of spaces, connecting spaces of the same color on a suitably checkered board.