Another theme is the relationship between Dib and Zim. In many fanfictions, their rivalry either intensifies or takes on a new form. It could be that they have to team up against a new threat that emerged because of the Florpus.
One great 'Invader Zim: Enter the Florpus' fanfiction is 'The Aftermath of the Florpus' on FanFiction.net. It explores what happens to the characters after the events of the movie in a really interesting way.
Often, there's a theme of self - discovery. As Female Zim is a different take on the character, she might be on a journey to figure out who she is in this new form. Also, the theme of adaptation is common. Just like in the original where Zim has to adapt to Earth, Female Zim may have her own unique ways of adapting, whether it's to Earth's environment or to the reactions of the other characters around her. And there's also the theme of power. How does being female change Zim's perception and use of power? This is something that many fanfictions like to play with.
It depends on how you look at it. Some fans consider the comics canon because they continue and enrich the storylines from the show. However, others might have reservations based on personal interpretations.
You can start by finding a collection or anthology of Invader Zim comics. Many bookstores or online platforms sell them. Then, just open the book and start from the first page.
Well, it's a bit hard to give an exact number. Different publishers and creators have come up with various Invader Zim comic offerings over the years. You might have to do some research to get a precise count.