Actually, most references to the term "pronunciation" in this site could be confusing. In any case, it should be specified what kind of pronunciation is being meant.
In this case, at least three meanings are possible:
- the ancient pronunciation in Greek and Latin - the new Greek pronunciation - the traditional English pronunciation
My comments are given below. The traditional English pronunciation is excluded from my considerations.
In contrast to modern English, the spelling rules in Greek and Latin are very simple. E.g. final "E"s should be heard.
For the new Greek pronunciation, we are to trust native Greeks.
Greek names are known by their Latin spelling (transliteration). For the ancient pronunciation in Greek and Latin, we can trust native Italians, in greatest degree. Anyway, each letter may usually have just one phonetic value. E.g., "X" is always "ks", never "kz" or "z". Similarly, "S" is always "s", never "z" in the ancient pronunciation. In the new Greek, "S" sometimes is "z" and "X" is "kz" sometimes. There are no such cases in the list of discussed names, however.
There are special Greek letters for "TH" and "CH" whose ancient pronunciation is not feasible to people speaking any modern European languages. Therefore, we have to use the modern Greek and/or English pronunciation. Only the voiceless English "th" (as in "three") should be used for "TH". For "CH", the usually proposed "k" can only be an approximation. Another approximation can be the sound "x" which exists in new Greek, Slavic languages, Hungarian or Turkish. Some people say the same sound should be heard in Scottish "loch".
The stress position is very important for the pronunciation of Greek names. We can rely on Native Greeks about it. In Greek spelling, the stress position is marked.
The length of vowels was also important. Now, it is feasible to native Italians only. For modern Greek, only the length of "E" is of some imortance: the anciant long "e" is pronounced as "i" (English "ee") now.
Greek names have different forms in Nominative and in the other cases. Sometimes, the Nominative form is shorter in the number of syllables.