How does Zwifts route planner take into account individual rider preferences, specifically in terms of customizing route elevation and terrain profiles to simulate real-world routes, and is it possible to upload and share custom routes with specific elevation and terrain characteristics. Considering the existing method of selecting a route based on distance, intensity, and type, does the route planner use any algorithms to ensure the route elevation and terrain profiles are accurately simulated. When creating a custom route, how can riders input their specific preferences for features such as hills, sprints, and turn density, and does the route planner prioritize these preferences over other factors such as route distance and intensity.