How to plot the phase plane for a system with three degrees by using streamslice?

For a system with 2 degree, we can use steamslice to plot phase plane.

e.g：

ODEs

dx/dt=x^2-2x-xy;

dy/dt=y^2-4y+xy;

Matlab code

[x,y]=meshgrid(linspace(-10,10));

streamslice(x,y,x.*(-2+x-y),y.*(-4+y+x));

xlabel(‘x’);ylabel(‘y’);

When I have a syetem of odinary differential equations with three degrees, how to plot phase plane of two degrees by using steamslice?

e.g：

ODEs

dx=f1(x,y,z)=-x

dy=f2(x,y,z)=-y+x^2

dz=f3(x,3,z)= z+x^2

I want to plot a phase plane of (x,y) by using streamslice. Is there a way to do this?

Thanks!