There's no contradiction: you can own the land, if you *create* it. You can't, really. Thus, you cannot really own it.

Happy to hear, that left-wing anarchism and AnCap agree on the practical level. Then we have no problems with it.

ZAD — one week? You know, that many people lived there four years together? Ukraine — obviously not today's, I'm talking about year 1917. Spain — years 36-39. If you want today day's example, search for EZLN, Christiania, Rojava, Aura Amba and others. 

Still waiting for the answer about hundreds of AnCap existing / existed territories by the way, you ignored that question.