Question: Simulation of a solution of Neutral Delayed Differential Equation

ddesys := {diff(x(t), t, t) + 2/25*diff(x(t), t) + 4*x(t) = 1/25*diff(x(t), t, t)*piecewise(t - 6/7 < 0, cos(t - 6/7), x(t - 6/7)) + 2/3*diff(x(t), t)*piecewise(t - 6/7 < 0, cos(t - 6/7), x(t - 6/7)) + 5/2*piecewise(t - 6/7 < 0, cos(t - 6/7), x(t - 6/7)), h(t) = diff(x(t), t, t), x(0) = cos(0), z(t) = diff(x(t), t), D(x)(0) = -sin(0)}

tdsn := dsolve(ddesys, numeric):

plots[odeplot](tdsn, [[t, x(t), color = red]], 0 .. 20, labels = [t, ""]);

Hello,
I wish to make a simulation of a solution of  Neutral Delayed Differential  Equation (second order) whose initial condition is the history function cos(t) for t <0.
unfortunately Maple considers the history function as a constant and not a function, the simulation I tried to do by Maple is therefore not good.
Could somebody help me please ?