\[- 4\frac{3}{8} \cdot \left( - \frac{4}{21} \right) = \frac{35}{8} \cdot \frac{4}{21} =\]
\[= \frac{5 \cdot 7 \cdot 4}{2 \cdot 4 \cdot 7 \cdot 3} = \frac{5}{6}\]