Is there a quicker way to expand

[sharp jacinth]

There has to be a quicker way to expand this if you are wondering why I am still on imaginary numbers it's because I just transferred to further maths on the last day of term ( forgive my autistic looking alphas btw)

[sinful nymph]

You can expand it in terms of a and b, where a = 2 - 3i and b = 2 + 3i
So it expands to z^2 - (a+b)z + ab
Then you can sub in the complex terms, cancelling out the is (for ab you can easily expand them using difference of 2 squares)