"Jsou ty mašiny velké a dlouhé?"

Translation: Are the machines big and long?

[markscheck]

I used Are they big and long machines? Not sure if this is different.

[endless_sleeper]

It is different. Predicative vs attributative adjective.

[VoolfiaDre]

Why we can't use "those" instead of "the"?

[VladaFu]

You can use either. If you have a problem with some translation not being accepted, you must report the complete sentence. If you are sure your sentence is correct, use the report button instead of the discussion. Be sure to always double- or triple-check for possible typos (extremely common).