Once you take the money out of the bank, it comes out to zero on their accounts, but you have $900 in cash in your hands.  So money has been created.

The reason that money has been created is that the $900 you borrowed was not just taken from someone else's account and given to you.  The $900 that you have in your hands now was just money that the bank "made."  It was able to create that money because someone else had deposited money in the bank.

So, the fact that the bank's books come out to zero on this loan does not mean money has not been created.  Money has been created because the money in your hands did not exist before the loan was made.