Visit Zero Point, Yumthang Valley, HotSprings and Back to Gangtok.
Again start early morning to avoid traffic.
This will eb a terrible place, and you will love it.
Fully covered with white snow.
Enjoy Maggi, hot tea alcohol at the highest point.
Try: You can drink boiling tea and you won't hurt yourself.
While on your way back visit Yumthang Valley, and enjoy the piece, with the music of river.
Drive back to the base of Gangtok.
*Shop only if you can bargain well.