I want to create a network of raspi 0's connected to Ethernet. Can I connect them all to one Ethernet wire via a USB hub?
The Raspberry Pi Zero has no ethernet port but only a usb port. You cannot plug an ethernet cable into a usb port. You need an ethernet to usb dongle for each RPi0. In this dongle you can plug in an ethernet cable but there is no way to connect all ethernet ports from the RasPis to only one ethernet wire. You have to use a switch with as much ports as you need. Now you can connect each RasPi with one cable to a free port on the switch.
With the prices you may consider to buy RPi3B or RPi3B+ with built in ethernet port.
You can also configure the microusb port on the raspberry pi as an ethernet port and connect the ethernet cable to one of the raspberry pis (using USB to ethernet gub). You can then configure the WiFi module as an access point/hotspot and have the other raspberry pis connect to this access point.