In order for this specific route to work trains will have to route via either Deventer or via Amersfoort. If the train goes via Deventer it will have to change direction two times: first time in Deventer and then a second time in Zwolle. If the train goes via Amersfoort it will have to change direction there as well. So both options are not the most convenient of choices. As there's already a train going from Amersfoort to Leeuwarden it would simply be best to just change trains there.

If you are talking about establishing a complete new railway, take into account that this is extremely expensive. It will be difficult to come by the necessary funds for such an undertaking and I think that there won't be enough passengers for a new line in these parts of the country as well. Also there's alot of nature and national parks around the region of Apeldoorn, so one does not simply start building some rails there.

Until 1950 a direct railway line (The Baron's Line) existed from Apeldoorn via Vaassen, Epe and Hattem to Zwolle. Due to low passenger numbers, increasing use of cars etcetera, the railway line then closed to passenger traffic (just like many other minor train lines in the Netherlands, with hindsight this is regrettable in my opinion) and in later years all the tracks were removed. It was substituted by bus services, which by now are almost only used by students. Train travelers to and from Apeldoorn have to make a detour and change trains once or twice via Deventer or Amersfoort in order to reach Zwolle and beyond.