Solution (source code)

= Solution

The coefficients follow by differentiating the same monomial:
$$
d(x^2y^3z^4)=2xy^3z^4dx+3x^2y^2z^4dy+4x^2y^3z^3dz.
$$
Thus this <exact differential form> has
$$
\boxed{f(x,y,z)=x^2y^3z^4+C.}
$$
Exhibiting a global <scalar potential> proves exactness directly, without needing an additional domain argument.