code: public static TileGrid tileGridZoom(TileGrid tileGrid, int fromZoom,
  			int toZoom) {
  
  		TileGrid newTileGrid = null;
  
  		int zoomChange = toZoom - fromZoom;
  		if (zoomChange > 0) {
  			newTileGrid = tileGridZoomIncrease(tileGrid, zoomChange);
  		} else if (zoomChange < 0) {
  			zoomChange = Math.abs(zoomChange);
  			newTileGrid = tileGridZoomDecrease(tileGrid, zoomChange);
  		} else {
  			newTileGrid = tileGrid;
  		}
  
  		return newTileGrid;
  	}
docs: Get the tile grid starting from the tile grid and current zoom to the new
  zoom level
  
  @param tileGrid
  current tile grid
  @param fromZoom
  current zoom level
  @param toZoom
  new zoom level
  @return tile grid at new zoom level
  @since 2.0.1