We're finally getting to the point where Nougat software updates are coming at a steady clip from manufacturers. ASUS is getting in a few for its midrange phone hardware - just last week we saw the ZenFone 3 Deluxe get its software update (that really should have come out in December at the latest). Now it's the non-deluxe model's turn, specifically the ZE520KL and ZE552KL variants. Those are the 5.2- and 5.5-inch versions of the unlocked GSM phone, if you haven't memorized the alphabet soup of those model numbers.
The OTA releases were announced on ASUS' ZenTalk forum, so they may or may not actually be going out to phones right this second. According to the release notes, there are quite a few tweaks to the ASUS Android build beyond the 7.0 upgrade, including better touch performance and removing redundant apps like Asus Share and PC Suite. The interface has some other tweaks for general speed and usability. Notably, the volume options for the ringtone and notifications are no longer linked.
ASUS says you'll need at least 1.5GB of free space on your phone to take the update, and it may be a week (or more, natch) before the rollout reaches all customers. At the moment we haven't seen manual downloads for either phone, but check your favorite user forum and you might see them pop up.