Question: solve the sys of ODE of diff(x(t),y(t),z(t),t) and substitute the solutions then plot diff(z(t),t) agains t

the following maple code is to solve the SYS of ODE x',y',z'

then plot z' agianst t

i got confused each plot give me zero

N:=1:M:=sqrt(N*(N+1)):N1:=1+N:w:=10:f:=1;
                             f := 1

ini1:= x(0)=0.5,y(0)=0.5,z(0)=0;
            ini1 := x(0) = 0.5, y(0) = 0.5, z(0) = 0
var:={x(t),y(t),z(t)}: 
dsys:={diff(z(t),t)=-(N1+M*cos(2*w*t))*z(t)-1+f*(x(t)+y(t)), diff(x(t),t)=-(N1-I*w-2*M*exp(-2*I*w*t))*x(t)-f*(N1+(z(t)))-2*f*M*exp(2*I*w*t),diff(y(t),t)=-(N1+I*w-2*M*exp(2*I*w*t))*y(t)-f*(N1+(z(t)))-2*f*M*exp(-2*I*w*t)}:
zd:=diff(z(t),t);
                                d      
                         zd := --- z(t)
                                dt     
res:=dsolve(dsys union {x(0)=0.5,y(0)=0.5,z(0)=0},numeric,output=listprocedure):
tit:=sprintf("F=%g,N=%g",f,N):

P1:=plots[odeplot](res,[[t,(zd)]],0..6,axes=boxed,titlefont=[SYMBOL,14],font=[1,1,18],color=blue,linestyle=1,tickmarks=[3, 4],font=[1,1,14],thickness=2,titlefont=[SYMBOL,12]);