1. They're lighter than the '04-'05 Zondas by 70 gm. total. Campy specs them as:
~ '03 Front, 740 + '03 Rear, 920 = 1660 gm.
~ '04 Front, 770 + '04 Rear, 960 = 1730 gm.
Which makes the '03s nearly as light as the approx. 1600 gm. Eurus'. Remember that Eurus has the Ti pawl carrier where Zonda is steel, so the main weight loss for Eurus is in the hub, not the rim, and the 4 less front spokes.
The "real" weight of my '03s are 762gm. Front/916gm. Rear = 1678gm. No lockring, skewers, rim tape. Not bad especially the rear, and only 2.9% off (F) & .5% (R) off from the factory spec.
2. The '02-'03 Zondas have aero spokes like Eurus. '04-'05 Zondas have round spokes.
3. '02-'03 Zonda front has G4 spoking which,
_a. Has 20 spokes rather than '04-'05 Zonda & Eurus 16 spokes, probably resulting in a stronger build overall, with little if any aero penalty.
_b. The '02-'03 front's G4 pattern is alternating radial & 1x, (10 spokes laced radially, 10 laced 1x) probably resulting in a slightly stronger build, yet somewhat more forgiving wheel than the all-radial Eurus and newer Zonda (radial) fronts.
The G4 front as such has better handling characteristics IMO than the straight radial-laced Z or E, especially on fast downhills. I've ridden all 3 of these front wheels.
4. The '03 Z has different hub shells than '04 Z. Neither is "better" in this respect AFAIK, just that they're differently shaped.