Nitro Cold Brew is made by storing Cold Brew coffee in a keg where it is combined with nitrogen and then served, producing the characteristic foamy and creamy texture. Nitro Cold Brew is normally a long drink.
Espresso Cool is extracted under pressure (unlike Cold Brew) and in a very short amount of time (like an espresso). However, the pressurization that happens during this extraction, forces air to mix with the cold extracted coffee and creates a texture and mouthfeel which resembles very closely that of Nitro Cold Brew, in a recipe which is almost the size of an espresso.