Hyesook's apartment is a gem! It is a mere 10mins luggage-friendly walk from Zurich HB on flat ground. We never needed to take the public transport to anywhere in Zurich since the main town is a short walk away and inter-city trains are very assessible. Just beside the train station is a bus station where you can book day tours and board buses to other cities too.
Do note that you will need to carry your luggage up a flight of stairs to reach the apartment. The apartment is spacious and you feel right at home immediately. The kitchen has everything you need, smart TV with Netflix in the living room, clean bathroom with a great hot shower, and washer/dryer works as described too.
Thank you Hyesook for the prompt communication and her lovely daughter Sora for receiving us and showing us into their lovely apartment. I'll highly recommend anyone visiting Zurich to stay here!