The visa is usually tied to the passport number, so you have to bring along the expired passport. The TIMATIC rules are also very clear on that:
Valid e-visas (Electronic Travel Authorizations- ETA) issued against a passport that has expired are accepted if the passenger travels with the expired passport together with a valid passport of the same nationality. It applies when:
- the passenger already travelled with the ETA and has an ETA immigration stamp on the expired passport; or
- the ETA has not been used and there is no ETA immigration stamp on the expired passport.
https://www.emirates.com/de/english/...destination=in
Also noteworthy is that the US has a similar requirement... you have to carry the expired passport that has the valid visa with you
