DOSBOX Pure mount CUE image with BIN+MP3

Hello I have converted a DOS game CDROM with audio to BIN+MP3 files in a folder, to reduce the size of the CD image. (as explained in dosbox manual I can mount this CUE image without problem with DOSBOX staging or Dosbox-X, and play the game with music. But I cannot manage to mount the CUE file in Retroarch DosboxPURE : message “Unable to open CD-ROM image file” and the name of CUE file. As advised in forum I have tried to zip it and name it with .DOSZ extension : i can mount it with Retroarch change disk command, but then the game does not recognize it. Am I doing this wrong, or DosBoxPure doe sot allow a “disk” with mp3 files ? Thanks for help