"Where is New Zealand?"
Translation:Ble mae Seland Newydd?
No. 'Adverbial' question words such as Ble/Lle, Pam, Sut, Pryd? (where, why, how, when?) are always followed by mae..., bydd..., roedd..., etc rather than by ydy/yw..., fydd..., oedd..., etc. (Althought the r- in forms such as rwyt, roedd, etc is sometimes dropped in speech.)
Thank you very much for the clarification!
In lesson "Extend1" e.g. there is "Beth yw ei farn?" Maybe "beth" is from another category of interrogative pronouns?