I think this issue of getting blood to the where it's needed is so very important and often neglected mostly because it's so difficult as well. I mean it's amazing that your body is filled with mostly water/blood but the tendons and fascia still have a hard time of getting nourished and lubricated.
My personal opinion is that its probably best to go easy on the cardio until you can get 'the blood' (or your 'chi') to traverse a greater area of the body so that the heart is not working tirelessly but effortlessly which is dependent on how much you have progressed in Zhang Zhuang.
It's also important for the purpose of avoiding pitfalls like tearing fascia that is dry and hasn't had ample supply of blood, hernias etc.
The path is fraught with perils
