Zanzarino should give credit to Final Fantasy for this card.
Pretty obvious connection IMO.
This same thing comes up with almost every single new card.
The fact is that there are basically no more new ideas in any games, especially in CCG's, because of the huge card pool of games like MtG. No matter how "unique" your idea, someone somewhere has already done it in some shape or form.
Related to this,
ideas are not copyrighted. Lets say I was the first person ever to create the concept of Paladin. Does that mean that every time someone uses the word Paladin in a game, they have to give me credit for coming up with the idea? Of course not because that would be silly.
This card has two parts. The name "Silence", and the mechanic of not letting your opponent play any cards. Both of these ideas have been used a million times before since the dawn of computer gaming, and saying that Final Fantasy came up with it, is again, silly.
I love the card. My #1 favorite strategy in all games is to annoy my opponents. It makes the victory that much sweeter.
Silence works perfectly towards that goal, so I will definitely be using this card.