How about making the night different from the day, aside from just having slightly lower visibility? To start off, the night isn't dark enough; you can still drive cars without any lights on without encountering any issues. Flashlights don't light up well enough inside buildings. Additionally, let's increase the danger during the night – greater risks leading to greater rewards type of deal.
In other games like Dying Light, many players (myself included) completely avoided nights due to the high level of danger from Bolter zombies and the real fear that comes with hearing them nearby, chasing you. Perhaps consider implementing this aspect as well with some unique night zombies, a zombie horde, or something that would make day and night distinctive from each other, adding an extra gameplay element (for free).
You could even allow players to sleep through the night, especially during the early stages of the game when you aren't equipped well enough to survive.