My understanding is that an in-spec USB-C power supply will supply 5V by default - then, upon negotiation with the client, can go up to a higher voltage.
In the case of the Zimaboard, this is basically a 12V barrel jack with a different shape. It just dumps 12V out on the pins with no negotiation or considerations of the client device.
I suspect if the downstream device was already 12V compliant, it might survive, but I wouldn't count on that nor would I be willing to test it.
USB-C must deliver a minimum of 3 amps at _at least_ 5V. If it delivers more than 5 amps it must contain a marker chip. The Zimaboard charger could deliver 4 amps at 12 v for 48 watt power delivery and be entirely within spec. (I haven't actually confirmed if this is what they do, so take it with a grain of salt)
In the case of the Zimaboard, this is basically a 12V barrel jack with a different shape. It just dumps 12V out on the pins with no negotiation or considerations of the client device.
I suspect if the downstream device was already 12V compliant, it might survive, but I wouldn't count on that nor would I be willing to test it.