Well, they might have a deep conversation about their different views on the world. Eren could try to convince Zeke of his more radical approach to saving the Eldians, while Zeke might push back with his own ideas of euthanasia for the Eldians. It could be a very tense encounter.
They could start to plan a strategy to deal with the Marleyans together. Since both have their own experiences with Marley, they might come up with a complex plan involving Titan powers and political manipulation. For example, using Zeke's position as a Marleyan weapon and Eren's influence within Paradis.
Levi sees Eren as a complex and unpredictable character. He recognizes Eren's potential but is also wary of his intense and sometimes uncontrollable nature.
You can start by looking on popular fanfiction websites such as Archive of Our Own. There, you can simply search for 'grisha' and a whole list of fanfictions will come up. You can then sort them by popularity, rating or length to find ones that might interest you.
One possible plot could be that they initially face a lot of shock and disbelief. Their friends and family have mixed reactions. Some are supportive, while others are worried about how it will affect their future, especially their dreams in the entertainment world. They then start to plan for the baby, with Zeke being really protective of Sharpay.
The baby could bring them closer. They'd have a new shared responsibility, which would strengthen their bond. They'd be more focused on each other and the family they're creating.
Eventually, Eren might start to investigate the reasons behind Mikasa's betrayal. If he discovers that there are more complex factors at play, like she was forced or there was a misunderstanding, he could feel a mix of guilt for his initial reaction and relief that their relationship wasn't as broken as he thought. However, if he finds out that she truly betrayed him out of her own will, he might become even more determined to carry out his plans, whatever they are, without her.
It could be Sharpay's over - controlling mother who is more concerned about her daughter's image and career than the pregnancy. She might try to convince Sharpay to take certain actions that are not in the best interest of the baby or Zeke.
Well, Zeke and Zeb in a Pulp Fiction - inspired story could have a number of possible significances. They could be symbols of the seedy underworld that Pulp Fiction often portrays. For example, they might be the guys who are always on the periphery of the main action, but still manage to get caught up in it. Maybe they are the ones who know all the secrets of the criminal underworld but are too afraid to share them. Or perhaps they are the comic relief in a very dark and violent story, like some of the characters in Pulp Fiction who provide a bit of light - heartedness in the midst of all the chaos. They could also be used to explore different themes such as loyalty and betrayal, as they might be friends who turn on each other when the stakes are high.