There are a little more Tianjin and Shandong in the north, and the better ones may be Long Yuan Hydraulic, Changyu Lihua and so on.
Other fields include Xinkui Hydraulic, Xiamen Yin Hua, etc.
Sany's subsidiary is Loudi Zhongxing Hydraulic Parts Co., Ltd. Zoomlion's subsidiary is called Hunan Teli Hydraulic Co., Ltd., and Xugong's hydraulic parts are called Xugong. The above three companies look at the size of their parent companies.
Which is the biggest? There is no standard, so I can't say.