Neither easy nor difficult type of trekking can be known as moderate trek in Nepal Himalaya. Basically, this sort of trekking exceeds 3500m and reaches up to 5000m high above the sea level. Normally, it takes 5-7 hours of walking in the Himalayan zone of Nepal. The trail may be parallel sometimes or ups and downs and may need to walk for more than an hour. But it is sure that there is no so steep pathway.
Similarly, the climate may not be very challenging, but it depends on the zone where you are having trekking. The poor weather can make the trail very difficult as well.
The Physical fitness of the trekkers is not strongly required for this moderate trekking Nepal Himalaya. However, the normal jogging and walking would be very helpful for this moderate walking trail in the hilly region of Nepal.
The easy to moderate treks in Nepal can be operated up to 15 days. It can be on the basis of either camping or lodging like home stay. The Everest Base Camp Trekking is the example of best moderate treks in Nepal which is the home stay based trekking trail.