H1b RFE : H1B transfer went to RFE but i have rejected the offer anyways

H1b visa RFE:
H1b transfer was applied by Employer Z but they delayed my joining date so I accepted and joined offer from Employer A and they filled new H1b transfer , so now Employee Z 's H1b transfer is in RFE . What should I do now or Employer Z do now ? is it a concern for my Employee A’s transfer petition ?

Let employer Z know that you wont be joining them so that they can withdraw the H1B application.
This shouldn’t affect your employer A H1B transfer application.

Also in future avoid joining on receipt, instead join after the transfer is approved to avoid issues with your status.