1. conda config --set allow_conda_downgrades true
2. conda install conda=4.6.11
3. conda create -n env_zipline python=3.6
4. activate env_zipline
5. conda install -c Quantopian zipline (at this point, if I import zipline, I'll encounter the issue mentioned above)
6. conda install python=3.6.8=h9f7ef89_0
7. pip install tables==3.5.2 (at this point, error change to 'ValueError: numpy.ufunc size changed, may ind ted 216 from C header')
8. pip install numpy==1.16.1