If the D stands for split as others here has stated. Then why have multiple users stated their symbols have changed also but not to ZIPZD. The broker said they were delinquent not what they were delinquent about. It could be a delay in the certs being sent to the brokerage or the clearing house.
It just does not appear to be a standardized process unless it is up to the broker to decided on what the symbol change should be for a stock in the middle of an R/S.
I am new to this so just asking because I do not understand how firm A gives ZIPZD while firm B gives ZIPZX firm c gives ZIPZ1982