Easiest place to get this is in the galata districtt. Reach on the top of the building with the only memior page in galata district. Collect the page and jump off the top. Press X for the parachute and fly around that area as there are lots of ziplines so u have enough options to get one. As u come close to zipline and when u r right above it press B.
Haha, Kage, I did the same thing. Dropped from the parachute, bounced off the zipline, and couldn't for the life of me figure out why Ezio didn't grab the damn thing!
I got it on my first trial.