What Visa/travel docs do I need to come to Zhuzhou to visit friends for a few weeks?

A tourist L is ok, but you need to get an invitation letter from your friends if you will stay with them on their places without hotel booking. Or, you can simply apply with return ticket and hotel bookings if you do not have invitation letter from any of your friends.

what docs I need to come to Zhuzhou to visit friend for a few weeks

If your friend sends you an invitation letter, you just need to provide your passport, filled application form and a recent photo. If not, round-trip air tickets and hotel booking are required.