Question

What is the polynomial function of least degree with integral coefficients that has zeros 2 and 3i?

Answer 1

To find the polynomial with the least roots, multiply all the zero terms together

If the roots were 1, -5, and 7, you could find it by expanding
(x - 1)(x + 5)(x - 7)

Answer 2

But with yours, you have an imaginary term. One of the rules with imaginary terms is that if b*i is a root, then -bi must also be a root.
So, your final zeroes are:
2, 3i, and -3i