Is xy^-2z^2 equivalent to xz^2/y^2 in simplification?

[Gringo123]

Simplify:

x⁴yz³ / x³y³z

My answer was:
xy^-2z²

However, the correct answer appears to be:

xz² / y²

I know that y^-2 is the same as 1/y² so would my answer still be marked as wrong in an exam?

 

[HallsofIvy]

Unless the problem specifically said "write with positive exponents only", it certainly should not be. Of course, I can't say if it would be or not!