It was definatelly in use by Plato (d 348 BCE) and Isocrates (d 338 BCE). however, the dating proves nothing because of all the classic tests missing and because the use of "philo" for love and "sophos" as wisdom date from much earlier and the use of build words using either date (all the way back to linear B).
So because the exact phrase "φιλοσοφία" may not predate your dating of "the Zarathustrian influence" but that does not argue for its origin in Zoroastrianism. First, the classic Greek works you have cited in the past never explain what the groups of Magi were or what Greeks adopted them. Second, the "over the top" criticism of Persians and the Persian Empire would seem to support a pretty huge cultural basis (especially among the philosophical classes) against all things Eastern. Third, the texts used to prove "Zarathustrian influence"are actually written a little later than the earliest use of "φιλοσοφία"). Fourth, even if "love of wisdom" was first used as a phrase in Zarathustra, that does not mean that it evolved separately in the Greek mind (the same conjunction were possibly used even earlier in Chinese, so by this logic, Zarathustra borrowed it from the Chinese) and what is meant by "φιλοσοφία" is quite distinguishable from "lord of wisdom". Oh, Thales slightly predates the conquest of Lydia (one to five years before the conquest to one year after, depending on what estimated date of death and date of conquest is used). His work was done well before the conquest.
