death date was 25 Nov 2015
LXC3-4MQ already has that death date. LFZN-ZN6 is "not found", I'm guessing because it is marked "living" and therefore currently only exists in your private space on FS's family tree.
If my guess is correct, you need to do two things: mark the profile in your private space as deceased, and then merge it with the other profile.
For the first task, go to https://www.familysearch.org/tree/person/details/LFZN-ZN6 and click "edit" next to the Death field (in the Vitals box). In the resulting "Edit Death" popup, click the circle next to Deceased. You can enter the date and place if you want, but these will go away in the next task, so I see no point. It may, however, require a reason statement; if so, any character will satisfy the requirement. (I usually just type a period.)
For the second task, go to https://www.familysearch.org/tree/person/details/LXC3-4MQ and click "Merge By ID", in the Tools section of the right-hand gray strip. Type or paste LFZN-ZN6 into the box and click Continue. Follow the instructions on the screen to complete the merge. (It has three steps: compare, combine, and explain. Dunno how the steps are actually labeled; I do too many merges to pay attention to the instructions and labels.)