\[ \left \{x'(t)=4 x(t),y'(t)=x(t)-2 y(t),z'(t)=x(t)-4 y(t)+z(t)\right \} \] ✓ Mathematica : cpu = 0.0069895 (sec), leaf count = 94
\[\left \{\left \{x(t)\to c_1 e^{4 t},y(t)\to \frac {1}{6} c_1 e^{-2 t} \left (e^{6 t}-1\right )+c_2 e^{-2 t},z(t)\to \frac {1}{9} c_1 e^{-2 t} \left (e^{3 t}+e^{6 t}-2\right )-\frac {4}{3} c_2 e^{-2 t} \left (e^{3 t}-1\right )+c_3 e^t\right \}\right \}\] ✓ Maple : cpu = 0.24 (sec), leaf count = 50
\[ \left \{ \left \{ x \left ( t \right ) ={\it \_C3}\,{{\rm e}^{4\,t}},y \left ( t \right ) ={\frac {{\it \_C3}\,{{\rm e}^{4\,t}}}{6}}+{\it \_C2}\,{{\rm e}^{-2\,t}},z \left ( t \right ) ={\frac {{\it \_C3}\,{{\rm e}^{4\,t}}}{9}}+{\it \_C1}\,{{\rm e}^{t}}+{\frac {4\,{\it \_C2}\,{{\rm e}^{-2\,t}}}{3}} \right \} \right \} \]