You can use the df[[colname1, colname2, colname3...]]
syntax to select the columns you want and then call .product
on that:
>>> df = pd.DataFrame({"A": [2,2], "B": [3,3], "C": [5,5]})
>>> df
A B C
0 2 3 5
1 2 3 5
[2 rows x 3 columns]
>>> df[["A", "C"]].product(axis=1)
0 10
1 10
dtype: int64