I’d say that you might also try doing your slice-and-save in ParaView first … to see if the files are any smaller. What you did is what I would have tried first (meaning I don’t know a lot more than you do).
Also, rather than clipping screenshots, you can mark down your code with triple single quote characters (‘’') to make nicer-looking blocks of code:
void nicer() {
std::cout << "nicer looking, right?" << std::endl;
}
There are lots of pages about Discourse markup around.