Whoocus

a1 = [1,2,3,4,5]
a2 = [[1,1,],[2,2],[3,3],[4,4],[5,5]]

a12 = a1.zip(a2)
p a12    #=> [[1, [1, 1]], [2, [2, 2]], [3, [3, 3]], [4, [4, 4]], [5, [5, 5]]] 

a21 = a2.zip(a1)
p a21    #=> [[[1, 1], 1], [[2, 2], 2], [[3, 3], 3], [[4, 4], 4], [[5, 5], 5]]