Well, it's hard to say. The story is full of surprises and twists, so it's difficult to predict Maki's fate exactly. You might want to keep up with the latest chapters to get the definite answer.
Zoro could react in a rather gruff way. He might say something like 'Nami, are you out of your mind?' But deep down, he might be secretly flattered. After all, Nami is an important person in his life. He'll probably need some time to process this unexpected turn of events and think about what it means for their relationship, both as nakama and potentially something more.
Luffy would be over the moon. He loves new adventures and a new baby on the ship would be like a new kind of adventure for him. He'd probably want to play with the baby all the time. Sanji would be a bit jealous at first because he has a crush on Nami, but then he'd also be really happy for them and cook all kinds of delicious food for the new mother and baby. Usopp would be making up all kinds of tall tales about the baby's future, like how the baby will be the greatest pirate ever.
The crew's reaction would be mixed with shock and joy. Franky would start building baby - friendly gadgets and cribs for them. Brook would be playing soothing music for Robin and Zoro to keep them relaxed. At first, some of the crew might be worried about how this would affect their adventures. But overall, they would come together. For example, Zoro's tough - guy image might change a bit, and the crew would tease him good - naturedly. Robin, being the more reserved one, might be a bit embarrassed by all the attention at first, but she would appreciate the love and care from the crew.
Well, in such a fanfiction, there could be various hints. Maybe Zoro's behavior might be more in line with typical female characteristics described in that specific fictional world, like being more empathetic or having different social interactions compared to the original male - character version. But it really depends on how the author has crafted the story.