How to use zpk for symbolic transfer function?

Hi How to use the zpk (zero-pole-gain ) command for symbolic transfer function?

Thanks

[David Chaparro]

This code gives the factors of the denominator.

syms s 

Phi=inv(s*eye(FIL)-A); %Matriz de transición
h=C*Phi*B; %Función de transferencia.
H=expand(h)
[N,D] = numden(H)
D_fact = factor(D,s,"FactorMode","real")
[Fil Col] = size(D_fact)

for a = 1:Col 
    coeffs(D_fact(a),s)
end