Zipp rims are made in the USA and all wheels supplied to us have been assembled in the USA.
Zipp use uni-directional carbon fibre for the majority of the rim resulting in lower weight. Woven carbon is used where the rim is drilled for spokes and also provides better impact resistance for the tire bed.
Zipp rims have a patented 'bulge' and dimples (similar to a golf ball) which makes them better aerodyamically
All Zipp spoked wheels use Sapim CX-ray oval spokes which produce less drag than round or bladed spokes.
The bearings used in Zipp wheels are custom made in Switzerland and are round to 10 millionths of an inch. This is five times rounder than most other bicycle component manufacturers. Zipp alos specify a teflon retainer to seperate the bearings. Most other manufactures spec brass retainers which introduces more wear and friction.