One option is to use numden:
syms Zta
Q = [(1/4 + 1/4*Zta) (1/4 - 1/4*Xi)]/(1/4)
[N,D] = numden(Q)
produces:
N =
[ Zta + 1, 1 - Xi]
D =
[ 4, 4]
Another option is to simply divide whatever quantity you are referring to by (1/4).
Example:
syms Zta
Q = [(1/4 + 1/4*Zta) (1/4 - 1/4*Xi)]/(1/4)
produces:
Q =
[ Zta + 1, 1 - Xi]
