On polynomial progressions via transference

We prove new cases of reasonable bounds for the polynomial Szemer\'{e}di theorem both over $\mathbb{Z}/N\mathbb{Z}$ with $N$ prime and over the integers. In particular, we prove reasonable bounds for Szemer\'edi's theorem in the integers with fixed polynomial common difference. That is, we prove for any polynomial $P(y)\in \mathbb{Z}[y]$ with $P(0) = 0$, that the largest subset $A\subseteq [N]$ avoiding the pattern $$x, x+P(y),\ldots, x+ kP(y)$$ has size bounded by $\ll_{P,k}N(\log\log\log N)^{-\Omega_{P,k}(1)}.$