It seems like you've begun to group and factored out the GCF.
Because the inner binomials (the ones in parentheses) are the same, the next step is to rewrite the equation like so:
(25-x^2)(y+1)
From here, we can further factor (25-x^2) since they are both perfect squares.
(5+x)(5-x)(y+1)
No further terms can be factored so that is the final answer. Hope this helps!