The format is a compressed numpy format, here is the Python code required to load the data from the file.

import numpy as np

filename="From-zebra.cnf-635-0.npz"

ax=np.load(filename,allow_pickle=True)['arr_0'].tolist()
Q=ax['Q']
const=ax['constant']

After executing this code, one gets in the variable "Q" the QUBO matrix , and in the variable "const" the constant that needs to be added to the evaluation of a solution against Q to get the values in the original space of the problem. Do not forget to amend the variable filename to match the file you want to load.