X^3 + y^3 + x^2z + yz - xyz và x^3 + x^2y - x^z - xyz

It seems you have provided a series of polynomial expressions and may want to categorize, simplify, or compare them in some way. However, the request isn't entirely clear.

Here’s a brief overview of each expression you've listed:

1. **\( x^3 + y^3 + x^2z + yz - xyz \)**
- This is a polynomial in three variables (x, y, z).

2. **\( x^3 + x^2y - x^z - xyz \)**
- Another polynomial, involving \( x \), \( y \), and an exponential term with \( z \).

3. **\( x^3 + y^3 + x^2z + yz - xyz \) (repeated)**
- This is identical to the first expression.

4. **\( 3x^2 + 6xz + 3z^2 - 3y^2 \)**
- A quadratic polynomial in terms of \( x \), \( y \), and \( z \).

5. **\( x^2 - 1 \)**
- A simple quadratic polynomial in \( x \), which can be factored as \( (x - 1)(x + 1) \).

6. **\( x^3 + 8 \)**
- A cubic polynomial that can be factored over the reals as \( (x + 2)(x^2 - 2x + 4) \).

7. **\( 4x^2 - 9 \)**
- A difference of squares, which can be factored as \( (2x - 3)(2x + 3) \).

8. **\( 4x^2 - 9y^2 \)**
- This can also be considered a difference of squares, factored as \( (2x - 3y)(2x + 3y) \).

If you would like to perform a specific operation (like addition, multiplication, finding a common factor) or need further clarification on any of the expressions, please provide additional context or specific questions!