It is interesting that your question only focuses up to part 8, and yet divides the book into two sections up until that point. (If you divide the book differently, of course, the answers would differ here.) Because you actually ask your question twice, I assume you are looking for two separate events/passages that connect to each other. As a result, I will give you a group of ideas, then focus on one for this particular answer and focus on yet another for the second answer.
What follows here are events in the earlier chapters followed by events in the later chapters that serve as connections. In the earlier chapters, Max begins to use Hitler's book as a blank canvas for his own, and in later chapters Liesel and Max both begin to write a book together and eventually Liesel receives Max's sketch book as a gift after he is forced to leave hiding. In the early chapters Liesel's foster family begins hiding Max (a Jewish man) in the basement, and in the later chapters Max teaches Liesel to read and causes quite a stir when the Nazis search the basement (even thought Max isn't found). In the earlier chapters, the mayor's wife is "nice" to Liesel by letting her peruse her library, and in the later chapters Liesel steals books from that library and finds a letter in the dictionary from the mayor's wife who knows Liesel is doing so (and invites her back in a more moral manner). In the earlier chapters, Liesel's foster father Hans is against the Nazi Party which he proves by teaching Liesel to read and by hiding a Jewish man in the basement, and in the later chapters that same Hans is forced to join the Nazi party.
Let's explore further the character of Max and how he uses books to reach Liesel. In part 3, Hans is given a copy of Hitler's Mein Kampf and soon after Max begins painting the pages white to use as a blank canvas for a book about his own being a member of the Jewish religion and having to go into hiding. Why does Max do this? Max does this because not only is he a wonderful human being but he is also "giving back" to Liesel who feels such compassion for Max that she gives him "presents" (of things like feathers and toy soldiers and newspaper) and offers him stories, the most coveted of which are about the weather outside (that Max never, ever gets to see).
The sky is blue today, Max, and there is a big long cloud, and it's stretched out, like a rope. At the end of it, the sun is
like a yellow hole.
Then later in part 5, Max and Liesel begin to write a book together: The Word Shaker from the newly ripped and painted pages (again from Mein Kampf). An even further connection to the later part of the book you mention (part 8) is that after Max escapes, he leaves her a gift of his "sketchbook," those special pages that they worked on together of The Word Shaker (about the power of words) as well as some other stories about his family and his thoughts about Hitler.
Please see my second answer for some other expanded thoughts in connection with the two parts of the novel you name.
Because you have asked a similar question here, I assume you would like a second event or passage from parts 1-4 that connects to parts 5-8. In my first response I gave some general ideas of connected events (gave an extensive example of Max's and Liesel's use of books), and I promised to provide at least one more extensive response here. I have also included a link to your first question in case you would like to peruse my response further.
How about exploring the relationship of the mayor's wife and Liesel in regards to the library? In parts 1-4 we find the mayor's wife being incredibly generous to the "poorer" child named Liesel by allowing her to come in (while she either picks up or drops off the laundry) and look at all of the books in the mayor's library. Then in books 5-8 we find Liesel reacting to her negative reaction against the Nazis by stealing the books from the very same library (in order to provide stories to Max, the Jewish man hiding in Liesel's basement).
After another ten minutes, the gates of thievery would open just a crack, and Liesel Meminger would widen them a little further and squeeze through. ***TWO QUESTIONS*** Would the gates shut behind her? Or would they have the goodwill to let her back out?
As Liesel would discover, a good thief requires many things.
Stealth. Nerve. Speed.
More important than any of those things, however, was one final requirement. Luck. Actually. Forget the ten minutes. The gates open now.
Of course, Liesel continues her "job" as the book thief in this regard and she eventually finds a letter in her latest book (a stolen dictionary) that indicates the mayor's wife knows Liesel's antics and wishes her to come back to the library in a more civil way.
Another area we can explore fully in parts 1-4 is how Hans was always seemingly against the Nazi part from the beginning.
"I am not violent. I am not malicious. I am a result."
Not only does he teach Liesel to read, but he also hides Max Vandenburg (a Jewish man) in his basement in order to save him from certain death. These decisions catch up with Hans in part 8 when Hans, himself, is required to join the Nazi army.
I think that in generating a list of events from the first four parts that can be seen in the second four parts, one event that threads both together is the role of death. Death is the central narrative force and voice in both parts. Death is seen in the first four parts in how he establishes the setting and backdrop. In the second four parts, his presence is magnified, in terms of the amount of death present. The costs of war and the presence of Auschwitz are both examples of how death has an accelerated role in the second four parts of the narrative. The presence of death, as an event, is important because it accentuates the brutality of war and the death count that accompanies it. This would be one event that can be connected between both parts.
I think that another part which can be connected between both parts is how Liesel struggles with aspects of her identity. In the first four parts, Liesel is finding ways to cope with the loss of her family and her own sense of self. Estrangement is a part of this process, something which is seen in the second four parts. In these parts, Liesel strives to think about Max when he leaves as well as her own past. Liesel trying to better understand her own place in the world is an event that connects the first four parts of the book to the second four parts of the book. It is a significant event because it shows how human beings are driven to question their own place in the world, regardless of the difficulty of conditions surrounding them. It is also significant because it shows how Liesel's insight is a consistent part of her characterization in both frames of the novel.