The zoom button could be a "press and hold" type of button. While you are pressing it, the example would be shown is bigger size. When you release the button, the effect disappear.

Maybe a zoom button alongside with the already existing buttons of "grammar", "translation" and "edit". It would be a fourth button. Extremely important for the examples sentences, which have a small font compared with the main word of the card.

Hey Zoltán Fodor (and other voters),

Could you tell what screens are you talking about and what languages?

The thing is that increasing fonts causes increased number of complaints about text not fitting cards etc.

But once we will gather more feedback about what screens are problamatic and what languages, we can try to improve it.