14. \( (2 x y)^{2}\left(-3 x^{2}\right)\left(4 y^{2}\right) \)

To simplify \( (2xy)^{2}(-3x^{2})(4y^{2}) \), we begin by breaking it down. First, calculate \( (2xy)^{2} \) which gives us \( 4x^{2}y^{2} \). Now, we can multiply this by the other terms: \( 4x^{2}y^{2} \cdot (-3x^{2}) \cdot (4y^{2}) \). Now, let's multiply the constants: \( 4 \cdot (-3) \cdot 4 = -48 \). Then, combine the \( x \) and \( y \) terms: \( x^{2} \cdot x^{2} = x^{4} \) and \( y^{2} \cdot y^{2} = y^{4} \). Putting it all together, we get \( -48x^{4}y^{4} \). So, the simplified expression is: \[ -48x^{4}y^{4} \]