c: \(=\left(a^2-b^2\right)\left(a^2+b^2\right)\left(a^4+b^4\right)\)
\(=\left(a^4-b^4\right)\left(a^4+b^4\right)\)
\(=a^8-b^8\)
d: \(=\left(a+c-b\right)\left(a+c+b\right)\)
\(=\left(a+c\right)^2-b^2\)
\(=a^2+2ac+c^2-b^2\)
e: \(=\left(x-y+2\right)\left(x-y-2\right)\)
\(=\left(x-y\right)^2-4\)
\(=x^2-2xy+y^2-4\)