Product of z1z2 with z1=1+i and z2=4i in standard and trig forms

[purplestar002]

Ok i am having a hard time with this one. Find the product z1z2 in standard form. Then write z1 and z2 in trig form and find their product again. Finally, convert the answer that is in trig form to standard form to show that the two products are equal.
z1= 1+i, z2= 4i​

 

[Integral]

Wow, this is a tough one!

It's your homework, why not show us what you can do with it?