I contacted Zeiss last year about weather sealing and they confirmed that there is none, unless you buy the more expensive, bespoke, industrial series. Having said that, the same lack of weather sealing applies to my medium format Mamiya lenses and my large format Cooke, Nikon, Schneider & Rodenstock lenses, all of which have been used in light drizzle.
Zeiss glass for both medium and 35mm format is excellent but again choosing it is also a personal matter depending upon what you seek to obtain from a specific lens. I also rate certain Mamiya lenses very highly. With the Zeiss ZF series I would avoid the 25mm but think the 21mm and 35mm f2 are superb lenses. The latter is certainly an improvement on the excellent Nikkor 35mm f1.4, and around the same price.
Just as a curiosity note, my digital has a Zeiss zoom lens with 12 elements in 10 groups, 4 lenses are aspherical.
Originally Posted by Rol_Lei Nut
This lens is a real jewel :D.
So the non-aspherical bias might be limited to only certain lens designers ;)
Consider something like a Nikonos if you need something weatherproof.