First, let's expand the expression:

(1-5x)(1+5x) = 11 + 15x - 5x1 - 5x5x
= 1 + 5x - 5x - 25x^2
= 1 - 25x^2

(3x-1)^2 = (3x-1)(3x-1) = 9x^2 - 3x - 3x + 1
= 9x^2 - 6x + 1

Now, we can rewrite the expression as:

(1-5x)(1+5x) - (3x-1)^2
= (1 - 25x^2) - (9x^2 - 6x + 1)
= 1 - 25x^2 - 9x^2 + 6x - 1
= -34x^2 + 6x

So, the simplified expression is -34x^2 + 6x.