LACHUNG, YUMTHANG VALLEY & ZEROPOINT.
From Gangtok its approx 100kms travelling. It takes 4 to 5 hours ride. But it won't be boring as there are many waterfalls in between the journey that you don't want to miss. For ex. Seven sisters waterfall. Plus the scenario is so beautiful around that you will not resist clicking it if you love taking pictures.
After reaching lachung, i stayed overnight and continued my trip the next day. Everyone at my hotel was up early. We all left around 5 in the moring for Yumthang Valley and Zero point.
There are small stalls/ shops at Yumthang Valley from where you can take on rent boots and sweaters/jackets. Price are quite nominal.
Note: - boots will be helpful only if there is snow/ snowfall. As I went in the month of October. I found it useless.
From Yumthang valley to zeropoint it's an hour journey. It's one of the most beautiful places I have witnessed in Sikkim. There is also NATURAL HOT WATER point in-between from Yumthang to Zeropoint. Localities call it 'Hot Spring point'. You can just ask your driver to take you there if it wasn't planned in the list. Though it won't be exciting for you if you have seen Surya Kund at Yamunotri (Uttarakhand).
Same day I came back to Gangtok. I reached around 8o'clock at night.