Writing lyrics to foreign songs is mostly easy, you just need to get the timing and syllables correct. It just takes a while is all. However, trying to write English lyrics to a Vocaloid voice ain't the most pleasant thing. For one thing, the pitches are pretty high, so it' kind of tricky to hit some notes. Then again, my voice is still developing, I'm pretty sure some adult sopranos could hit those notes. Anyway, it was very time consuming and a bit tricky, but I was able to write lyrics to the song "Triple Baka."
I found a karaoke version on youtube, so my only real dilemma is trying to record my voice and match it with the mouth movements. Wooooo I get to play voice actor♥