The coordinates of C and D you mentioned have no fixed value, but they are above the median vertical line.

Where the coordinate X5 of point E = (x1+x2)/2; y5=(y 1+y2)/2

If e is the midpoint of CD, X5 = (x3+x4)/2 can also be obtained; y5=(y3+y4)/2

If CE=DE= fixed value is known, the C and D coordinates can be obtained.