Well, definitely not z. Not long after an actual z, it clearly doesn't sound like that. I get the v version though, especially on speakers.
But, to be fair, it's still more "rendőr" than anything else imo. One may argue that it could be better articulated or the recording could be better - but it's definitely legit, nothing particularly flawed or rare about it. It's just good enough not to be within the 10 most important things to complain about regarding this course. :)
To elaborate on the answer a bit: article usage differs between the two languages. "Milyenek angol rendőrök" doesn't even sound grammatical while "az angol rendőrök" can refer to both a custom, context-defined group of police officers (that is, "the English police officers") and the "trivial" group of them - that is, all of them, in general.
The word rendőr is a policeman, rendőrnő means policewoman, rendőrség means the police organisation, respectively the police station. Before WWII they has been called csendőr (csendőrnő, the female version never existed, because at that time women were not accepted). Officer means tiszt, but it is not used in everyday's parlance since you barely find one on the street.
Before WWII they has been called csendőr
Actually, csendőr was a different organization, not a different name for the same thing. It was the Hungarian version of gendarme (they were also known as zsandár which comes from that word). So it was a military institution that had police functions, mostly in villages. And this was replaced by police exclusively - although I wouldn't be surprised if this would be changing soon, I think this topic is turning hot.