Question

the variable Z1 and Z2 are defined as z1 equals 6i+3i and z2 equals 10 + 8i which expression is equivalent to Z1Z2

Answer 1

If you multiply the two numbers, you will have 36 + 78i.
*I assumed you had a typo in the first expression, it is generally written as 6 + 3i. If you meant, 6i + 3i, it should have been just 9i.

To find this product, we use the foil method.

(6 + 3i)(10 + 8i)
60 + 48i + 30i + 24i^2
60 + 78i + 24(-1)
34 + 78i