\displaystyle{\lim_{x \rightarrow 0+}\frac{x - \sin x}{(\sinh x+x^3)^2} = \lim_{x \rightarrow 0}\frac{x - \sin x}{(\frac{x}{x}\sinh x+x^3)^2} = \lim_{x \rightarrow 0}\frac{\frac{x - \sin x}{x^2}}{(\frac{\sinh x}{x}+x^2)^2}}