Just a quickie. There were two EZ 40s, the Zeiss one and the Askania one. The one pictured in Mike's first reference is the Zeiss one and it was rejected for its "instability". The 2nd reference shows the Askania EZ 40 and it is the one that was installed in 5 Fw 190s of II/JG 300 in the summer of 1944. It's problem was that mounting the gyro at the back of the gunsight made the RLM consider it too bulky, and so for the EZ 42 two gyros were mounted in a unit in the fuselage.
Hope this helps,
George
PS. There have been threads on the EZ 40/42 in the past few months. That's how I found out about the EZ 40. The latest is at
http://forum.12oclockhigh.net/showthread.php?t=11427