Full Synchronisation Requirement - Perform an Air Assassination from a zipline
Head straight down, keeping your distance from the Janissaries who shouldn’t engage you directly unless you attack them or there are no other a targets for them around.
When you reach the port, climb the leftmost building to find a zipline, which will take you over a couple of targets on the ground before it reaches its rooftop destination. Just wait for the option to assassinate them to appear, and then do so to ensure you get full synchronisation. Fight off anyone near the objective area, and then turn on Eagle Sense to find the trail. Follow it and watch the scene. After Ezio somehow managed to not notice the two Janissaries in the roof with him, run instead of fighting. Leap from the dock platform to the wooden poles in the water, and hop across them to slow down your pursuers. Climb the tower at the end of the next dock and use the zipline (where you’ll have another chance to take out a target for full synchronisation).
When you reach the shipyard, move through the skeleton of a ship under construction and use one last zipline to reach solid ground, finally. Then, head east to the objective marker to end the Memory.