I recently moved to Zurich in my third trimester of pregnancy, and I've been wowed by the great OB experiences I've had so far.
I'm seeing Dr. Jochen Eichler for my general pregnancy needs in the Zurich Oberstrass (office directly next to Seilbahn Rigiblick). I picked his practice because it was one of the few I saw with a great, comprehensive English website.
http://www.frauenarzt-dr-eichler.ch/
He's thorough, kind, and both he and his staff speak perfect English. The practice feels very different than my American OB, where everything seems rushed.
Dr. Eichler referred me out to Prof. Dr. Boris Tutschek for a fetal doppler echo. Dr. Tutschek was also really thorough and easy to work with. He gave us a lot of detail about our baby, her heart (which looked fine!), and medical research and findings relevant to my pregnancy. His staff spoke English pretty well, but not as fluently as Dr. Eichler's.
http://praenatal-zuerich.ch/
I'd highly recommend either doctor.