This is what happens when everyone is given access to reply. Some dumb fellas like @rajgupta9011 think they know everything and start replying to questions without even understanding it.
Zerodha is my 4th demat account. In sharekhan, MyEspresso and Angel broking I was allowed to create my own user id even in 2014. How was it possible with those brokers? They had some special privileges? No, in all these brokers, client id and user id are completely different. This is the basic principle of software design. Client ids are used to uniquely identify users by the system whereas user ids are used by the customers for login purposes which is again internally tied to the client id. There is absolutely no necessity to have both user id and client id as same.