[latex] \frac{56 x^{3} y^{4} }{z^{5} } (- \frac{ x^{2} z^{4} }{16 y^{6} }) [/latex]

[latex] \frac{56x^3y^4}{z^5} *(- \frac{x^2z^4}{16y^6} )=[/latex] [latex]-( \frac{56x^3y^4*x^2z^4}{z^5*16y^6} )=-( \frac{14x^5}{z*4y^2} )=[/latex] [latex]-( \frac{7x^5}{z*2y^2} )=- \frac{7x^5}{2y^2z} [/latex]