For the first fraction
the numerator and denominator have unlike signs. So, the sign of the resulting fraction is negative.
For the second fraction,
both numerator and denominator are negative. Thus, the resulting sign of the fraction is positive.
Hence, the two fractions `(x^3z^3)/(-y^3)` and `(-x^3z^3)/(-y^3) ` are not the same.
Sorry for the slip. Take note of this correction.
The denominator of the two fractions should be `-3y` , not `-y^3` .
Still, when simplified, the two fractions are not the same.