Step 1: Recognize linear dependence directly:
Since $C_3=C_1+C_2$ (true entry by entry: $x+a$, $y+b$, $z+c$), the three columns are linearly dependent.
Step 2: A determinant vanishes whenever its columns are linearly dependent:
This is a standard property — no row reduction is even needed once the dependence is spotted.
Final Answer:
\[ \boxed{0} \]