✓ Mathematica : cpu = 0.0373917 (sec), leaf count = 551
DSolve[{Derivative[1][x][t] == 6*x[t] - 72*y[t] + 44*z[t], Derivative[1][y][t] == 4*x[t] - 4*y[t] + 26*z[t], Derivative[1][z][t] == 6*x[t] - 63*y[t] + 38*z[t]},{x[t], y[t], z[t]},t]
✓ Maple : cpu = 0.349 (sec), leaf count = 1145
dsolve({diff(x(t),t) = 6*x(t)-72*y(t)+44*z(t), diff(y(t),t) = 4*x(t)-4*y(t)+26*z(t), diff(z(t),t) = 6*x(t)-63*y(t)+38*z(t)})