Regard $y$ as the independent variable and $x$ as the dependent variable and find the slope of the tangent line to the curve $\left(5x^{3}+3y^{3}\right)^{2}-4x^{4}y = 60$ at the point $(x, y) = (1, 1)$.

The slope of the curve at the point $(1, 1)$ is equal to .