Trials Fusion is a side-on motorbike game. It is not a first-person shooter. In fact it's about as far from a first-person shooter as you're going to get. So it's magic that you can take the game's map editor and build a replica of Call of Duty: Zombies with it.
It took Pneumatic Bog three months to put this together, and it's now available to play on the Xbox One version of Fusion. Note that it doesn't just have a little bit of running around and shooting: he's got 18 weapons in there, eight perks, the mystery box and even AI for the zombies.
People have tried this kind of thing before (or gone in other amazing directions!) but we've never seen a shooter as fleshed-out as this before.
The map is called "COD Zombies Polar Darkness" if you're searching for it.