Liangzhu core zone is now open to public but with limit of 3000 visitors per day. They have 6 time-slots of max 500 visitors each. Also, buying of tickets can be done via wechat (it seems you need chinese ID card to buy). I will try buying online once slots are open or maybe just buy on-site. Reservations can only be done within a week schedule and it seems slots are easily filled up.
Here is the official website (only in mandarin): https://yuding.lzsite.cn/liangzhu_web/index.html#/OrderBuyPage/needtoknow