For me, Hebrew was harder than Greek. I took Greek first, however, and have heard that whichever one you take second is the hardest. Greek (especially the vocabulary) is pretty easy if you are good with your English and have a decent vocabulary. Also, Hebrew is much easier to forget. I have a longer get-caught-up time with Hebrew than I do with Greek.
Though I do not know much Latin (hardly enough to say that I am a beginner), it seems to me that learning it and Greek at the same time would not be that difficult. They are quite similar.

Lon