Господа! Пишите правильно: не Zenaida, а Zinaida (Зинаида)
Lord! Write correctly: not Zеnaida, and Zinaida (Зинаида)
I have seen it spelled both ways, and by some very knowledgeable people. The French spelling is "Zénaďde;" I'm guessing that may be the reason for the "Zenaida" spelling.
You are correct Dru. The majority of non Russian text books use the French spelling of Zénaďde, which has gradually become Zenaida, have even seen a few 'Zinaide'. While the correct spelling is Zinaida, I think the variations in pronunciation cannot be helped. It's the same with the variations of Yusupov (Yussupov, Yossopov, Iusupov, Youssoupov, Youssoupoff).