Fit
The heel of the Zealot ISO 2 is snug and cradles the foot well with thick padding at the ankle collar. The ISOFIT inner sleeve consists of very stretchable air mesh that contours to your foot for a sock-like feel through the midfoot, with thick tongue padding on top. Midfoot tension is easily adjusted and locked down with a traditional lace system using extensive FlexFilm exoskeletal overlays; some portions are connected to the upper, others are separate. Length is true to size. 

Comfort
All that padding around the heel and midfoot on the Zealot ISO 2 provide a comfortable ride without chafing, but they retain a lot of heat in warm conditions. Ventilation is further limited by the FlexFilm overlays in the midfoot, but the airmesh upper in the toe box breathes quite well. Underfoot comfort is exceptional, with a new 3mm topsole of EVERUN, Saucony’s highly durable and elastic cushioning material positioned close to the foot, on top of traditional EVA cushioning to dramatically diminish road impact. 

Responsiveness
Our testers found the Zealot ISO 2 to be soft but not super responsive, with much of the impact energy absorbed rather than converted to propulsion. Below the EVERUN layer is Saucony’s PWRGRID+ premium midsole material with high cushioning and durability. All of these technologies combine for a very soft ride, but not necessarily quick energy return. 

Ride Quality
The outsole is a new TriFlex design with zig-zagged horizontal flex grooves for improved forefoot flexibility; these also provide increased surface contact for stability. The rubber in the forefoot is injection blown for softer landing, and is 33% lighter than standard outsole rubber, although we found the grip slightly lacking in wet conditions. However, the flex grooves also give the outsole some nice versatility to venture off-road if desired. The Zealot ISO 2 rolls smoothly from heel to toe, with nice comfort throughout the stance cycle. 

Speed
The Saucony Zealot ISO 2 is built more as a high mileage trainer than a race day option, although it’s certainly capable of handling some tempo running. The extensive cushioning and comfort comes at the expense of quick responsiveness and fast leg turnover.