>>> import itertools
>>>
>>> x = [[1, 2, 3],
... [4, 5, 6],
... [7, 8, 9]]
>>>
>>> for i in itertools.product(*zip(*x)):
... if list(i) not in x:
... print(i)
...
(1, 2, 6)
(1, 2, 9)
(1, 5, 3)
(1, 5, 6)
(1, 5, 9)
(1, 8, 3)
(1, 8, 6)
(1, 8, 9)
(4, 2, 3)
(4, 2, 6)
(4, 2, 9)
(4, 5, 3)
(4, 5, 9)
(4, 8, 3)
(4, 8, 6)
(4, 8, 9)
(7, 2, 3)
(7, 2, 6)
(7, 2, 9)
(7, 5, 3)
(7, 5, 6)
(7, 5, 9)
(7, 8, 3)
(7, 8, 6)
>>>
и вправду в 2 цикла.