To find \(\frac{d y}{d x}\) for the given function \(y = 4(\tan x + \sec x)(\tan x - \sec x)\), we can use the product rule and the chain rule. First, expand the expression inside the parentheses to simplify the differentiation process. Then, differentiate the resulting expression with respect to \(x\).
Step 1: Define the Function
We start with the function given by
\[
y = 4(\tan x + \sec x)(\tan x - \sec x).
\]
Step 2: Simplify the Expression
Upon simplifying the expression, we find that
\[
y = -4.
\]
Step 3: Differentiate the Function
Next, we differentiate \(y\) with respect to \(x\):
\[
\frac{d y}{d x} = 0.
\]
Final Answer
The derivative of the function is
\[
\boxed{0}.
\]