Aahh, this show really brought back memories. I was an avid fan of Invader Zim, but with time my love for it waned. Seeing this sparked my interest, so I had to see ehat it was all about.
First of all, I love your art style. It's something completely different from Vasquez's distinct style from the show, and this isn't bad. It definitely adds a different flavor to it, which I'm sure is intentional, due to the spin on this story.
I can see that the main focus is going to be the horror aspect of Zim universe, which I am thoroughly intrigued by. The show, while mostly light-hearted and humorous was pretty dark, to the point I wasn't exactly allowed to watch it as a kid. I was a little disappointed there wasn't much humor thrown in there, but I can understand how that could be distracting if the story is meant to be taken more seriously than the original. In the very least, I found Dib's interaction with himself (fourth wall awareness?) was really amusing. I also like the pacing of the dialogue and narration. So far it's pretty solid. There are line breaks in almost every screen, but would it seem weird if I actually like this? I'm not sure if it would annoy others, but I think it adds more tension, as well as discourage me from just skimming it over. Also, I feel like it adds more to the fact that this is in Dib's perspective. However, I noticed that once a scene ends, it lingers on the last background for the scene before transitioning into the next one. Not a big deal, but in a longer playthrough I could see this becoming an issue to me, anyways.
The only major thing I feel could be improved on is the audio. The sound effects throughout were distracting to me, since the quality was poor in contrast to everything else. I think the music was very charming and in good quality. However, I feel that the style and tone doesn't really fit the genre, and isn't something I was expecting in something Zim-related. I know you had a friend who composed the music, and I don't mean this to knock down their good effort and talents or anything. I just think something more intense, and possibly techno would be better suited for this.
Especially at the point where Dib discovers the bodies in the closet. The soft violin/piano piece doesn't seem right in that scene.
I highly recommend going to jamendo, and just listening to different styles you think would fit it best.
Other than that, it was a really enjoyable game! I would really like to see more of this and what happens in the future. Even if you don't decide to continue this particular project, I would be interested in seeing any new VN's you decide to create. There is definitely potential from what I've seen. I hope I was helpful somehow, and I encourage you to continue with your stories. Cheers!