The center of the hyperbola is the midpoint of the line segment joining the foci, which is (1, -3).
The distance between the foci is 20, which is also the length of the transverse axis.
The distance between the center and the directrix is the distance between the center and the focus, which is 20/2.5 = 8.
The distance between a point on the hyperbola and the directrix is the distance between the point and the focus minus 8.
Therefore, the equation of the hyperbola is (y + 3)^2/64 - (x - 1)^2/256 = 1.