Zeiss is a well known brand name from the company named after it's founder, Carl Zeiss AG. According to the Ziess.com blog the company is changing its name to Zeiss to create consistency across its brand communications.
What does this have to do with Windows Phone? Well, Nokia uses Zeiss lenses in several of their Lumia Windows Phones, including the upcoming Lumia 1020/EOS. We've seen leaked images of the camera plate on the EOS that were branded with both "Zeiss" and "Carl Zeiss". Some have thought the images with the Zeiss label were fake.
It would appear that with the company name change these images are looking a lot more credible. Luckily it won't be long until things will come into better focus when we all expect Nokia to officially unveil the Lumia 1020/EOS/Elvis during the July 11th Zoom Reinvented press event.