Me too! I have had emoncms running on a Pi Zero (not recently though) as I thought a Pi zero + emonTx would make a great alternative to the emonpi, much cheaper and twice as many CT’s. (see 4 CT emonBase using emonTx and Pi Zero W) I do not recall any issues, but that was a self-built image not the emonSD image.
There have been at least a couple of instances where I have assisted users to get wifi working on a Pi zero W when using the emonSD, this is/was a bit of a pain for Pi Zero users as the usual Raspbian method of adding a wpa_supplicant.conf file to the boot partition before fitting SDcard to the Zero was not possible with the emonSD since it was a read-only OS. So I know others have used emonSD on a Zero, but maybe the difficulties getting a network connection setup (with no Ethernet port) was just too tricky for some?
A search for “Pi Zero W” gets quite a few hits Search results for 'pi zero w' - OpenEnergyMonitor Community
There is a current discussion about some issues with a self-built image currently, which happens to be on a Pi Zero, but I don’t think that is the reason for the issues directly. (see Strange issues on own built emoncms running on raspberry pi zero w)
I see no reason for it not to work fine, but the lack of Zero users (or feedback from them) means there may well be unresolved issues, if you try it, please report back either way. It would be good to hear if all goes well, but also if it doesn’t go so well we can help resolve the issues and perhaps improve things for the Zero users.