Userform: delete all content through double click but not the highlighted line

Hi,
I have a worksheet in whichs Column A Cells , there is corresponding string content in Col. Z. Some cells of column Z contain of many lines (up to 100 line) which i want to reduce to one. I want to select one line through double clicking in the listbox of the userform and all other lines should be deleted and only the clicked one should remain. Code should then jump to the next non empty Z cell.

Columns B, C, D, E, F, G and H should also be shown in the userform and they should be live editable. I have attached and example file with userform and example data.

I will be very thankful for each help.