Can I use pdepe to solve a nonlinear PDE system?

I'm trying to solve the following PDE system for ?(z,t) and v(z,t), using pdepe:

∂/∂z [(1/? + A)*∂v/∂z - v*∂?/∂z)] + [1/(1-?)]*[A*∂v/∂z *∂(1-?)/∂z - B*v/?^2] = 0

∂?/∂t = ∂/∂z[v*(1-?)]

where A and B are constants. The initial condition is

?(z,0) = 0.05

and the boundary conditions are

v(0,t) = 0

v(1,t) = - 0.1

The code I used is this [I use u(1) ≡ ? and u(2) ≡ v]:

function rbs
m = 0;
x = linspace(0,10,100);
t = linspace(0,10,100); 

sol = pdepe(m,@rbs_pde,@rbs_ic,@rbs_bc,x,t);
u1 = sol(:,:,1);
u2 = sol(:,:,2);

% --------------------------------------------------------------
function [c,f,s] = rbs_pde(x,t,u,DuDx)
c = [0; 1]; 
f = [((1/u(1)) + (1/0.75))*DuDx(2) - u(2)*DuDx(1); (1 - u(1))*u(2)]; 
s = [-(1/(1 - u(1)))*DuDx(1)*DuDx(2) - (1/8000^2)*(1/(1 - u(1)))*u(2)/(u(1))^2; 0];
% --------------------------------------------------------------
function u0 = rbs_ic(x);
u0 = [1; 0]; 
% --------------------------------------------------------------
function [pl,ql,pr,qr] = rbs_bc(xl,ul,xr,ur,t)
pl = [0; ul(2)]; 
ql = [0; 0]; 
pr = [0; ur(2) + 1e-1]; 
qr = [0; 0];

However, I get the following error message:

Spatial discretization has failed. Discretization supports only parabolic and elliptic equations, with flux term involving spatial
derivative.

[Bill Greene]

What are the boundary conditions for ?? Your first equation has a second derivative of ? with respect to z so you need two boundary conditions.