What is the relationship between Liaoning northern heavy industries Machinery Manufacturing Co., Ltd. and northern heavy industries Group?

It doesn't matter. Liaoning northern heavy industries Machinery Manufacturing Co., Ltd. is a private enterprise, and northern heavy industries Group is a state-owned enterprise.

Northern heavy industries Group Co., Ltd. (hereinafter referred to as northern heavy industries) is a large-scale state-owned company established on the basis of the merger and reorganization of Shenyang Heavy Machinery Group Co., Ltd. and Shenyang Mining Machinery (Group) Co., Ltd. These two enterprises are not at the same level at all.