ok so like is Zero straight because I heard if you drink from another blood you are saying you love them.

yes zero is straight. thats the reason y he craves yukis blood even tho kaname gave him some of his, is because zero likes her so u will only crave the blood of your love.

Well, drinking Yuuki's blood on its own doesn't mean that he's straight/heterosexual. Vampires will drink the blood of people they don't necessarily love - for example if they're starving, or if they're fighting that person. But given that Yuuki's the only person he's ever shown an interest in, we can assume that he is heterosexual.