The difference, by the numbers
Both have lime juice, dark rum and Angostura bitters. Only the Queen’s Park Swizzle has mint and simple syrup; only the Zombie has aged rum, falernum, Donn’s Mix, grenadine and pastis. In parts, a Queen’s Park Swizzle is 1 lime, 6 rum and 1 syrup; a Zombie is 4 rum, 2¼ rum, 1 lime, ¾ falernum and ¾ Donn’s Mix. By volume, the Queen’s Park Swizzle is 75% spirit, 13% syrup and sugar and 12% citrus; the Zombie is 68% spirit, 11% citrus, 9% liqueur, 9% mixer and juice and 3% syrup and sugar. That makes them close cousins on the ratio map.
The Queen’s Park Swizzle is the stronger drink in the glass (20.1% ABV against 17.8%), but the Zombie is the bigger drink, so it holds more alcohol (2.83 standard drinks against 2.07). The Zombie has more calories (about 330 against 242) and more sugar (11.1 g against 9.5 g). Both are served in a highball; the Queen’s Park Swizzle is swizzled, the Zombie blended.