Episode 0 is much more of an epilog to Part 5 than an opening for Part 6, even the character design is the same as that of Part 5 and not 6. In fact it probably should have been labeled as a short ova instead of a Part 6 episode. But it's a wonderful tribute to Kiyoshi Kobayashi. It's not action heavy but it's got great moments of the gang having fun, some unique interaction between Jigen and Zenigata and especially Jigen and Fujiko and it does a great job at dissecting the characters. Hearing Lupin call Jigen the only thing that's stable in his life is great. If I had to complain about something the whole drone thing was significantly less interesting than the rest of the episode (though thankfully it didn't take up a lot of time) and the animation feels a bit rushed (the episode was obviously made in short notice due to Kobayashi's retirement).
As I said this is not an opening for Part 6 so don't expect that, but it's an excellent start for the series in the new decade and a nice farewell to a man who has been voicing Jigen for 52 years!