List derivation equation in the square array

li=[[1,2,3],[2,3,4],[3,4,5],[4,5,6]]
xx=[[y*y for y in i] for i  in li]
aa=[y*y for i in li for y in i]
print(aa)#[1, 4, 9, 4, 9, 16, 9, 16, 25, 16, 25, 36]
print(xx)#[[1, 4, 9], [4, 9, 16], [9, 16, 25], [16, 25, 36]]