I believe there are two ways to interpret "survival"; whether it would be harder to get killed or harder to die. Basing my answer off of Max Brook's The Zombie Survival Guide, winter conditions removes one thread (namely zombies) and replaces it by another (winter).
First, why would the threat from zombies be alleviated? Well, first off we already, as coordinated human beings, have trouble travelling through snow; zombies, shambling, would have a lot more trouble than us, being uncoordinated and, you know, rigor mortis-ified. Additionally, if their body does not generate heat, they would probably freeze solid.
Now, why would winter become a problem? Well, we can split the zombie scenario into two different categories: the minor kind and the major kind. In the first case, the outbreak is limited to a small town or only to a few zombies, in which case they would probably be easily dispatched. However, the second case, where possibly our whole society breaks down, some basic necessities that we have come to rely on, such as electricity, would stop being available. How would you not freeze without heating? How would you get your food?
In short, it all depends on what you mean by "easier". Most likely, one problem (zombies) would be replaced by another (winter). Max Brook's World War Z: An Oral History of the Zombie War and The Zombie Survival Guide both contain elaborate sections on the dangers of winter survival in the event of a zombie apocalypse. I strongly suggest those two books for all zombie-related questions.
Hope this helps!