They have very similar meanings. "Death-mark'd love" is pretty self explanatory, and "star-cross'd lovers" are lovers that are fated for doom. This basically foreshadows the fate of Romeo and Juliet and what will likely happen to them due to their forbidden love. Unfortunately I don't have the prologue on me nor did I read it in a very long time, so I can't provide evidence. But that's basically what it is trying to say.
Personally, I've had to do a few of those before, and it's not fun.
I would recommend splitting up the work, if you have some extra time doing some more of it, not loading it all up on the last day.
And if you have any questions, don't just stay confused about it, search it up somewhere or ask it on Brainly.
If the packet has any explanation pages, I would also read those because those are helpful when completing the exercises.