I just gave it a try with piCore 9.0b1 on my zero w. Unfortunately wifi still seems not to work. I did install firmware and wifi extension.
On my pi3 everything works perfectly. I recognized on my zero that "brcmfmac" is not listed on execution of "lsmod" - while it is with my pi3.
Is there still a driver/module missing? Or was I mssing something oO