To simplify the expression (3-xy²)² - (2-xy²)², we can expand both squared terms and then combine like terms.

Expanding the first squared term:
(3-xy²)² = (3-xy²)(3-xy²) = 9 - 3xy² - 3xy² + x²y⁴ = 9 - 6xy² + x²y⁴

Expanding the second squared term:
(2-xy²)² = (2-xy²)(2-xy²) = 4 - 2xy² - 2xy² + x²y⁴ = 4 - 4xy² + x²y⁴

Now, we can subtract the second expression from the first expression:
(3-xy²)² - (2-xy²)² = (9 - 6xy² + x²y⁴) - (4 - 4xy² + x²y⁴)

Simplifying by removing the parentheses and combining like terms:
= 9 - 6xy² + x²y⁴ - 4 + 4xy² - x²y⁴

Combining like terms:
= (9 - 4) + (-6xy² + 4xy²) + (x²y⁴ - x²y⁴)

Simplifying further:
= 5 - 2xy² + 0

Therefore, the simplified expression is 5 - 2xy².