Optimize the following Python code by replacing the two for loops with one.
list1 = [1,2,3]
list2 = [4,5,6]
for i in list1:
  for j in list2:
    print(i * j)
list1 = [1,2,3]
list2 = [4,5,6]
 
for i,j in zip(list1, list2):
    print(i * j)