Is there any way to make this long if statement more concise?

Here is my long if statement:

   if i % 2 == 1 or i == 0:
       if x1 > x:
           ny = y + ceil(shift * (i / 2))
           ny1 = y1 + ceil(shift * (i / 2))
       elif x1 == x:
           ny = y
           ny1 = y1
       elif x1 < x:
           ny = y - ceil(shift * (i / 2))
           ny1 = y1 - ceil(shift * (i / 2))
       if y1 > y:
           nx = x - ceil(shift * (i / 2))
           nx1 = x1 - ceil(shift * (i / 2))
       elif y1 == y:
           nx = x
           nx1 = x1
       elif y1 < y:
           nx = x + ceil(shift * (i / 2))
           nx1 = x1 + ceil(shift * (i / 2))
   else:
       if x1 > x:
           ny = y - ceil(shift * (i / 2))
           ny1 = y1 - ceil(shift * (i / 2))
       elif x1 == x:
           ny = y
           ny1 = y1
       elif x1 < x:
           ny = y + ceil(shift * (i / 2))
           ny1 = y1 + ceil(shift * (i / 2))
       if y1 > y:
           nx = x + ceil(shift * (i / 2))
           nx1 = x1 + ceil(shift * (i / 2))
       elif y1 == y:
           nx = x
           nx1 = x1
       elif y1 < y:
           nx = x - ceil(shift * (i / 2))
           nx1 = x1 - ceil(shift * (i / 2))
   return nx, ny, nx1, ny1

I'm not sure if it's possible to just convert this whole thing into a simple equation. However, if not, is there any possible way to only have the first large if statement and make the sign in ny = y + ceil(shift * (i / 2)) be plus if i % 2 == 1 or i == 0 and minus else?