We may have some confusion. An inverter changes 12VDC to 120VAC to provide power to AC outlets, and depending on size, microwave. You would have a large bank of batteries if you had an inverter. I don't see an inverter listed in the CR information on Zingers.
The converter changes 120VAC shore power to 12VDC. That is the power that keeps the trailer battery charged, lights the lights, provides circuitry power to furnace and fridge, powers the water pump, etc. All 12VDC stuff. Very few trailers now have a 12VDC outlet, and if they do (like on my Z-1), it's only a low-amperage one on the Winegard powered antenna plate. (because the amplifier is also 12VDC).
There are a lot of people here who wish to have 12VDC outlets, in the form of the "cigarette lighter" plug, or otherwise, and you will find some discussions elsewhere in this forum. There are a lot of 12VDC appliances (fans, lights, televisions, etc) that could be used in a boondocking (no shore power) situation. Wiring (and fusing) will be on your own, and popular tap-off places are at the outlet of the converter or direct from the battery.
Marty and Martha
2015 Z-1 211RD
2012 Nissan Titan