df =
        N0_YLDF  ZZ        MAT
    0  6.286333   2  11.669069
    1  6.317000   6  11.669069
    2  6.324889   6  11.516454
    3  6.320667   5  11.516454
    4  6.325556   5  11.516454
    5  6.359000   6  11.516454
    6  6.359000   6  11.516454
    7  6.361111   7  11.516454
    8  6.360778   7  11.516454
    9  6.361111   6  11.516454

gb = df.groupby('ZZ')
[gb.get_group(x) for x in gb.groups]

df = [x for _, x in df.groupby('ZZ')]

def split(df, group):
     gb = df.groupby(group)
     return [gb.get_group(x) for x in gb.groups]