So I'm in the stages of rough drafting a fantasy/science fiction story that has been in my head for nearly 13 years. While I have written many private small stories for my friends, I have never written a story on this grand scale spanning multiple continents and cultures and tackling multiple themes in the story. Think A Song of Ice and Fire or A Wheel Of Time (call me suicidally overconfident or ambitious if you wish). So my issue I need advice on is I have two characters that are thousands of miles apart and each tackles a different issue of the world's setting with different goals and objectives. Both characters are essential for the overall narrative and I plan on having them meet at some point in the story where their goals converge, with each one tackling separate themes that contribute to the narrative and character development. However, one of the characters is doing something that will take them a long time to tackle compared to the central character we start off with. One character is following clues to find his mentor while dealing with a large conspiracy that may bring about the end of the world, while the other is solving issues on their continent that also has to deal with proxies of this conspiracy group and trying to get to the heart of the matter while also having their own goals and aspirations. However, the speed of their narratives is very different. The character following his mentor is dealing with problems as they come, while the other character is nation-building, dealing with science experiments, and scheming. Now the story starts off following the character looking for his mentor, it serves as a great introduction to the world and fresh eyes due to the character's naive nature. This creates a timeline problem. Should I throw more problems at the character looking for his mentor, or should I have dates that show different time frames with the two different characters (I'm worried this might confuse the reader or demand them to make homework by drawing timelines), or should I just follow the main character looking for his mentor while scrapping the other character's story for a narrative focus until they met up and go from there (I really don't want to do this because it would just compromise the story and sacrifice the narrative and themes), or maybe making a separate book series akin to a prequel or separate series that runs parallel to the main story (think Breaking Bad and Better Call Saul) but eventually combines into 1 story (but I'm worried this will confuse readers even more). Advice would really be appreciated here.