Pronunciation differences between pinyin 'zh' and 'ch', and between 'qi' and 'xi' Although this question states that these sounds can be often mixed (though mainly in dialtects...)

Do you know where I could find a detailed description of position and movement of the tongue 
for these consonants - so as to learn how to make it sound properly.

For example I have very much difficutly making a different sound between 中 zhong1 and chong2 虫... because I don't know how to make them sound different. I feel like the zh should be a little more stronger, exploding. But on several audio excerpts, the ch is also strong.

Idem, I would say that x is a little more windy, and q has a soft and really short 'k' at the beginning of the beginning of the sound... but that's not precise enough to make it sound right all the time.
The difference between zh and ch has nothing to do with the position of the tongue: these two are pronounced with the tongue in the same position; the difference is aspiration -- ch is aspirated while zh is not. Both are retroflex affricates.

x and q have less in common -- actually q and ch are much closer to an untrained ear, as they're both aspirated affricates -- the only difference being the position of the tongue, ch being a retroflex, and q an alveo-palatal. x on the other hand is not aspirated, and a fricative. Actually x is close to the German Ich-laut (except ch in Ich is a palatal rather than an alveo-palatal).