Translation:These are modern and efficient bicycles.
I think I know what he meant! "Ezek a modern biciklik!" by itself is an exclamation. You would use it to describe a sense of wonder or surprise or even anger, but that's where the sentence ends. For example some guys on modern bikes race past you, then you would say it as such!
I think I figured this out. The version I actually had in mind was "Ezek a biciklik modern es hatekony". But this is different, because "Ezek a" is followed by "biciklik". In our example this is not the case, so we need a standalone version of this demonstrative pronoun, which is "Ezek".
These modern and efficient bicycles is the way we see it, unfortunately. When there is uncertainty already regarding articles, it is VERY easy to get misled with a sentence ike this. It looks like a sentence fragment to non-Hungarians. We are expecting these "modern and efficient bikes" to do something, not simply be as it appears here.