If $\widehat{\text{i}}\times \left[\left(\overrightarrow{\mathrm{a}}-\widehat{\text{j}}\right)\times \widehat{\text{i}}\right]+\widehat{\text{j}}\times \left[\left(\overrightarrow{\mathrm{a}}-\widehat{k}\right)\times \widehat{\text{j}}\right]+\widehat{k}\times \left[\left(\overrightarrow{\mathrm{a}}-\widehat{\text{i}}\right)\times \widehat{k}\right]=0$ and $\overrightarrow{\mathrm{a}}=x\widehat{\text{i}}+y\widehat{\text{j}}+z\widehat{k}$, then the value of $8\left(x^3-xy+zx\right)$ is equal to