The first day I would build
Give the city one clear route before adding extras.
- Start with Ban Jelacic Square and Upper Town while energy is high.
- Use Dolac Market as the natural reset instead of crossing town too early.
the easier plan is Dolac Market and Ban Jelacic Square first, Upper Town next, museums or Maksimir when the day needs a softer pace. That keeps the day readable instead of turning every good name into a separate detour.
I would rather leave one place for tomorrow than drag a tired route through Maksimir Park just because it looked close on a map.