−i × 2i × 3i

[math_celebrity]

(-1 x 2 x 3)(i x i x i) = 6i^3
-6i^3 = -6 x i^2 x I

We know that i = sqrt(-1)
i^2 = sqrt(-1) x sqrt(-1)
i^2 = -1
-6(-1)(i)
6i