To simplify the expression, we can factor out -4u^4z^2 from each term in the numerator:
(-23u^4 z^2 +32u^7 z^7 -12u^2 z) / (-4u^4 z^2) = (-4u^4 z^2)(32u^3 z^5 - 8u^2 + 3) / (-4u^4 z^2)
The -4u^4z^2 terms cancel out, leaving:
(32u^3 z^5 - 8u^2 + 3) / u^4z^2
Therefore, the simplified expression is (32u^3 z^5 - 8u^2 + 3) / u^4z^2.