This is actually mathematically quite simple when you think about it.
The line AB as we shall call it is simply a vector comprised of an X, Y and Z component.
dX (the x component) = Bx - Ax
dY = By - Ay
dZ = Bz - Az
Let’s argue you were looking for the midpoint. Well, the midpoint is exactly halfway between A and B, and as A to B is a vector made up of components, the midpoint is half each component. (A + .5 * (B - A))
So, the same applies for any fraction of the vector. Thus, splitting it into six parts is just taking each sixth of the vector.
With mathutils (the default blender maths lib) we don’t even have to bother doing component operations, we can multiply the entire vector by a scalar:
from mathutils import Vector
a = Vector((0, 0, 0))
b = Vector((3, 3, 3))
difference = (b - a)
a_sliced = [(difference / 6) * (i + 1) for i in range(6)]