We would like to send push messages to a group of users all using Zoiper
Is it "push notifications" that you need or just 1 message to be sent to several SIP users?
I would like to sen 1 message to several users at the same time
If you want to send 1 message to several contacts from Zoiper - that is not possible.
If you have access to the VoIP server you could do that from it.