Game Asset Pipeline

I created a model in Maya, and exported it to ZBrush where I sculpted it, but now it is high-poly, and the asset is going to be exported to Unreal. I understand I need to make a low poly version but their seem to be many ways to do that. Do I take the original version and bake the high-poly mesh onto it? Do I retopo it in Maya? Do I do some strange ZBrush fuckery?

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All of these things are very confusing, and I don't understand the best way to do this. Anybody shedding light on the full game asset pipeline would be appreciated.