After an exhaustive search for the Zephyr Railroad's track gauge, I decided to find it indirectly. In short, I have confirmed that the Zephyr Railroad's track gauge is 24 inches using the picture below.
I researched the exact height dimension of that orange Igloo cooler to the left of the tracks and found that it is 23.25 inches tall (source: http://www.target.com/p/igloo-10-gallon-seat-top-beverage-cooler-with-cup-dispenser/-/A-10281492#prodSlot=medium_1_0&term=igloo+10+gal+cooler
). If you copy the part of the image with just the cooler and paste it horizontally over the tracks, it fits inside the tracks with about one pixel row to spare on each side. So, based on this analysis, we can infer that Zephyr Railroad's track gauge is less than one inch wider than the height of an Igloo 10 Gallon Seat Top Beverage Cooler, which equates to 24 inches. This is not surprising, as this is a very common track gauge for amusement park railroads, such as those using Chance Rides C.P. Huntington trains, which are all 24-inch gauge.
Feel free to tell me your opinion of this finding, and whether you think its genius, makes sense, or just nuts.