I agree absolutely with Siance and SuperCaz. When you're tired, or even just half-tired, after a run, you aren't going to get the best out of a strength-training exercise, and mental and physical fatigue may well interfere with your posture to the extent that you end up doing the exercises with poor form and getting injured.
The "fat-burning" low-intensity zone is a myth and, as you say, BiB, high-intensity exercise burns more total calories, and more fat, per unit of time. The most important factor is the distance you run. However, running at around 70% of MHR, or a perceived effort of "able to talk in short sentences", is easier to sustain, and less likely to lead to you becoming injured or stopping enjoying your runs, than belting out every session trying to cover the biggest distance in the time available.
How many times a week do you run?