You can start at either end .   For this solution, I started at the right-hand piece .

    Notice the loop is under the double-line of the cord    . . . . . move it along the piece towards the left . . . . .

                 . . . . . all the way to the end . . . . .                        . . . . .and through the second hole at that end . . . . .

    Wrap loop around second piece                                          start traveling along its length

    . . . . . to its furthest end                                               start to go over that end . . . . .

          come around the end . . . . .                                     and head back the way you started

    . . . . . going towards the second hole of the first piece . . . . .

      . . . . . almost there, go up through the hole                   now you're top side of the double-line cord

    . . . . . keep on traveling towards the start hole                                     and over it . . . . .                          

    . . . . . free the loop from the first hole . . . . .                                          and then the second                

You've now released the loop -- first half of the cord -- from the first piece entirely Simple enough to now free the rest of the cord from the second piece

You're done !   Congratulations !

                                                                                                                                                                                           

Great for displaying your prize puzzles in their special cabinets . . . . . and a plethora of many other uses as well

    “Puzzle solving is an art and a science, which involves the organization of patience and
  perserverence, within the framework of simplistic logic influences,
~ with a dab of intuitiveness and a slice of luck ~
for the purpose of effecting and augmenting creativity within an expressive matrix of  
    imagination and three-dimensional spatial stimuli .”