system speed call
As sunspark said, this is often a system speed call entry... make the dialed number 0 and the destination an extension, group, or key/LDN appearance. If you have an actual console, you can also make 0 an LDN appearance. You can also make 0 the DN of a group (hunt/ring), make it a multicall key, or create a phantom extension with key appearances. Each has strengths and weaknesses depending on how you want to route dial 0 calls, if you want to be able to pick them up with a dial code, route differently via day/night mode, etc.
