This is more a common routing issue than belonging specifically to Raspberry Pi. Anyway, here are the manual routing settings because I don't know what operating system and what networking service do you use. Look how to set it persistent on your setup.
We have one local area network 192.168.0.0/24 (bitmask
/24 assumed because you don't tell it) and will assume that the RPi 4B is connected to it with ip address 192.168.0.2/24 on its interface. This ip address must be static because we will use it as gateway interface that must be known. I also assume that all RPi Zero have its default route set to the RPi 4B (that's usually default). The RPi 4B is acting as a router and it knows where to send ip packets because the devices are all direct connected to it. I also assume that it has a default route to the internet router on the local network so it can get into the internet.
On the RPi 4B you have to set ip forwarding so that ip packages can be forwarded to the other interfaces if needed:
rpi4b ~$ sudo sysctl net.ipv4.ip_forward=1
If you can get into the internet on the management console (the computer on the local network 192.168.0.0/24) it has its default route also set to the internet router on the local network. You have to tell it to use the RPi 4B as default gateway instead:
mgmnt ~$ sudo ip -4 route del default
mgmnt ~$ sudo ip -4 route add default via 192.168.0.2/24
You should now be able to ping all devices and get into the internet. The internet connection is routed now by the RPi 4B because its default route is set to the internet router on the local network.