XZ-series of unmanned aerial vehicles in 2020

The XZ-series of unmanned aerial vehicles was initiated in 2014 initially as an endeavour of theoretical development of multirotor unmanned aircraft models. The idea and major work was done by the author of the current article, and now, by the year of 2020, the series is still in constant process of inventing new designs. Most of the models were patented at the Bulgarian Patent Office through patents for inventions or utility models. In the recent years, publications on the XZ-series models have appeared in foreign scientific journals with high scientific impact metric. The XZ-series of flying machines includes various types of multi-rotor machines such as standard multi-rotors, fixed wing multi-rotors and compound multi-rotors. This article is a concise guide, as concise as it can be, to the XZ-series of unmanned aerial vehicles as of middle 2020 and, as such, it shall be followed in the future by sequels, published regularly, summarizing the ongoing process of the XZ-series aircraft model development.