If the arguments are not as expected (e.g. arrays of different lengths, both scalars, not numeric) then null is returned.
arrayOrScalar1 * arrayOrScalar2
,
the same length as the input array(s)multiply(array(1,2,3), array(2,4,6)) = [2, 8, 18]
multiply(2, array(1,2,3)) = [2, 4, 6]