Zermatt is a great choice for autumn hiking in Switzerland, with beautiful fall colors and less tourists than summer.
However, you must plan carefully as lifts and services start to close in early October, meaning you cannot reach some trails. Plus you must monitor the weather and trail conditions as early snow can make some trails impassible.
This itinerary has our favorite hikes for autumn. We did these hikes around the 5th of October, which already had great fall colors and the lifts were still open.