x(y - z) + y(z - x) - z(y - x) is equal to:

1. 0

2. xy + yz + zx

3. xy + yz - zx

4. xy - yz + zx

x(y - z) + y(z - x) - z(y - x)

= xy - xz + yz - xy - yz + xz

= (xy - xy) + (- xz + xz) + (yz - yz)

= 0 + 0 + 0

Hence, option 1 is the correct option.