The three constructions
The storm flap is the reference solution: a strip of the shell fabric, sometimes stiffened, folds over or under the zip and takes the rain itself. Double storm flaps — one outside, one inside — appear on jackets built for the worst weather. The cost is bulk, weight and a two-handed operation.
The laminated zip replaces the flap with a water-resistant polyurethane coating over the coil — YKK's AquaGuard is the dominant example and appears by name in manufacturer specifications, including jackets in this database. It sheds rain well and enables the clean, light designs of modern shells. Its limits: the coating is water-resistant rather than absolutely waterproof, the slider is stiffer, and the join at the top of the zip needs a 'garage' — a small covered pocket — to stop water tracking in at the chin.
The water-resistant coil zip is the lightest variant, common on running and ultralight shells: a tighter coil with a lighter coating. It trades still more absolute resistance for weight and smoothness.
Which zips matter most
The main front zip takes the most direct weather and is opened most often, so its protection matters most. Pit zips sit under the arm, sheltered, and laminated coils are ample there. Pocket zips are the underrated leak path: an unprotected chest-pocket zip admits water straight into the jacket's interior, which is why better shells either laminate them or shelter them behind storm flaps or the front closure.
When assessing a jacket, the hierarchy is simple: main zip protected by a flap or a laminated coil with a garage; pocket zips laminated or sheltered; pit zips laminated. A jacket with a bare coil zip anywhere on its weather side is telling you something about its intended use.