Carl Zeiss Jena continued trading after 1945, it certainly didn't cease to exist, ownership changed when it was effectively nationalised but the machinery, designs, some of the workforce were the same. I have a 1950's CZJ 150mm f4.5 T (coated) Tessar that's identical to the first coated version made in 1938.
Originally Posted by E. von Hoegh
You also need to bear in minf that there was some early co-operation between the newer West German Zeiss set up by the Americans and CZJ, they expected to be able to reunite the company. This co-operation was stopped by the Communists in East Germany in the early 1950's.