The Zealot ISO 2 gains an ounce, but is also softer and more responsive.
As with most new 2016 shoe models from Saucony, the Zealot ISO 2 gets the Everun treatment. Everun is more resilient and has better energy return than other Saucony cushioning materials. In the Zealot ISO 2, Everun is placed directly under the innersole, as a “topsole”. This places the cushioning properties of Everun as close to the foot as possible. A change like this doesn’t always mean a change in feel. But in this instance, the Zealot ISO 2 does have a softer underfoot feel and it also feels more springy than the original.
Beyond the addition of Everun, the Zealot ISO 2 also gets a new upper and new outsole. The new upper results in the shoe fitting about a 1/4 size smaller than its predecessor. This means some runners will be fine with their usual running shoe size, but others will need to go up to the next half size. The forefoot width seems to be the same, as does the midfoot volume and heel fit. However, if you cinch the laces tightly, the Zealot ISO 2 distributes the pressure through the middle two sets of eyelets. This is an improvement over the original, which would concentrate the pressure beneath the bow of the laces.
It’s hard to say how the change in outsole design impacts the feel of the shoe, but it certainly doesn’t have a negative effect. Flex grooves are in different places than the original, but the depth of the grooves seems to be maintained. When Saucony updated to the Triumph ISO 2, the shoe felt firmer and I think the reduction in the depth of the grooves influenced that change. However, with the Zealot ISO 2, the outsole change may actually enhance the cushioned feel of the shoe.
All of the changes resulted in the Zealot ISO 2 gaining about one ounce in weight over the previous model, but it is not a heavy shoe. The shoe is also 1mm thicker in stack height, but maintains a 4mm heel-toe offset. As such, it’s great for logging daily miles if you are a forefoot or midfoot striker. It is light and responsive enough for long tempo runs as well. If you really want to pick up the pace, the Saucony Kinvara 7 is a better option.