I think it is important to remember that St. Justin Martyr was (IIRC) of the belief that all religions have some level of truth to them. Perhaps Zoroastrianism happens to have a lot of truth to it. It also is possible (at least from the Jewish stand point, I am not so sure what the Fathers say about it) that Zoroaster was in fact a prophet. After all, the consider Job (who they also consider to be a Gentile) to be a prophet. If Orthodoxy also believes in the possibility of prophets outside of Israel (the people not the place) before the coming of the Lord, then one could take the approach that Zoroaster may indeed have been a prophet.
Regardless, it is impossible to be an Orthodox Christian and not believe that at some point Zoroastrianism radically changed its doctrines, if it indeed had an origin in God, as it has radically different views from Orthodoxy on a number of points. Also, it is quite possible that it did have an impact on Judaism, for instance I recall reading an article some time ago (which had been on that computer's favorites on Firefox, until the computer stopped turning on and I lost everythign on it) in which a Rabbi admitted that it influenced Judaism. However, there isn't a particularly great reason to believe that any core beliefs of Judaism were changed (as I recall, the Rabbi - an Orthodox Rabbi by the way - mentioned only actions they do, and not beliefs), and also that if they were, there were many varities of Judaism until fairly recently. While now there is primarily Orthodox (which include a good deal of variety such as Modern Orthodox, Hasidic, Ultra-Orthodox, etc.), Conservative, and Reform Judaism, until the middle ages, there was also a large contingent of Karaite Jews (today they still exist, but are extremely small in number). During the time of the second Temple, there were a truely massive number of Jewish sects, from the Essenes, to the Phariasees (sp?), to the Sadducees, and several others most likely. While Zoroastrianism undoubtedly influenced many, the real question is, did it influence the Apostles and Christ Himself? I would have to say that if at any time the Apostles were - prior to becoming Apostles - incluenced by it, they were not by the time the Church was established on the day of Pentecost. That is the important thing to rembmer.