It's an accepted answer, if it wasn't for you please provide a screenshot if it happens again.
If the verb ends in a t, then zij is she. E.g. Zij drinkt. But if the verb ends in en, then zij is 'they'. E.g. Zij drinken. Hope that helps :-)
zij means she or they but since the verb is the full form (drinken) the subject must be plural here, so only they is correct.
"Zij" is the stressed form of "ze". When you're comparing different people, like in this sentence, you should always use "zij".
They drink tea, but I don't.