27x³ - 27x² y + 9xy²-y³ - 20x³ + 15x² y - 4xy² + 3y³ + 10x³ + 12x² y - 5xy² + y³

To simplify the expression, let's group like terms:

(27x³ - 20x³ + 10x³) + (- 27x² y + 15x² y + 12x² y) + (9xy² - 4xy² - 5xy²) + (-y³ + 3y³ + y³)

Combine the like terms within each group:

17x³ + 0x²y + 0xy² + 3y³

Simplifying further, we have:

17x³ + 3y³