Solve (x+2y-z)^7

$$( x + 2 y - z ) ^ { 7 }$$

Expand

$$x^{7}+560x^{3}y^{4}+35x^{3}z^{4}+840x^{3}\left(yz\right)^{2}+672x^{2}y^{5}-21x^{2}z^{5}+448xy^{6}+420xy^{2}z^{4}-84xyz^{5}+7xz^{6}+1680xz^{2}y^{4}-1344xzy^{5}-1120x\left(yz\right)^{3}+128y^{7}+280y^{3}x^{4}+280y^{3}z^{4}+1680y^{3}\left(xz\right)^{2}+84y^{2}x^{5}-84y^{2}z^{5}+14yx^{6}+210yx^{2}z^{4}+14yz^{6}+210yz^{2}x^{4}-84yzx^{5}-280y\left(xz\right)^{3}-z^{7}-35z^{3}x^{4}-560z^{3}y^{4}-840z^{3}\left(xy\right)^{2}+21z^{2}x^{5}+672z^{2}y^{5}-7zx^{6}-1680zx^{2}y^{4}-448zy^{6}-420zy^{2}x^{4}-1120z\left(xy\right)^{3}$$

Evaluate

$$\left(x+2y-z\right)^{7}$$