\(1,\left(x-2\right)\left(x+2\right)\left(x^2+4\right)-\left(x^2-3\right)\left(x^2+3\right)\)
\(=\left(x^2-4\right)\left(x^2+4\right)-\left(x^2-9\right)\)
\(=x^2-16-x^2+9\)
\(=-7\)
\(2,\left(6x+1\right)^2+\left(6x-1\right)^2-2\left(1+6x\right)\left(6x-1\right)\)
\(=\left(6x+1-6x+1\right)^2\)
\(=2^2=4\)