Ok so to start off with, after beating Zero Time Dilemma I'm going to have to say overall, the Zero Escape games for me rank like so:
999 > VLR > ZTD
In terms of story, I'd say:
VLR > ZTD > 999
In terms of gameplay:
VLR > 999 > ZTD


~~~~~~~~~~~~~~~~Spoilers After Here~~~~~~~~~~~~~~~~

I really enjoyed the majority of ZTD, once I started unlocking endings things got super interesting. A huge problem I had though (and I guess it's just because of the way I played the game) is that I didn't do a single escape (I think, maybe I did 1? But I don't think so) room after I unlocked my first ending. As much as I enjoy visual novels, and despite the fact that ZTD is a visual novel, this really wasn't something I was expecting, especially with the nature of VLR and 999.

On top of that, I found all the puzzles incredibly easy in comparison to its predecessors. Maybe I just got better at them? But a lot of the puzzles in VLR stumped me for awhile, and none of them in ZTD did.

I really enjoyed getting to watch Junpei and Akane reunite, I thought it was nice though a bit shallow. It felt as though one minute they were saying "I don't even know who you are anymore" and the next everything was alright. I get that they both still loved each other even though they felt the other had changed, but I felt like there should have been more communication between them before that jump to false engagement ringing. I still really liked it though, since I'm a sucker for romance.

I enjoyed the Sigma/Phi/Diana team WAY more than I thought I would. When I started the game I mainly thought I would be focused on Akane/ Junpei because of my affinity for them, and the fact that I didn't really like Phi/ Sigma all that much in comparison, but it really drew me in quickly. Granted I figured out the whole "plot twist" thing with Zero and Phi after a couple of bad endings with them, but D-End:2 still blew me away. When everything clicked into place: with Luna, Phi, Diana, the brooch, the blue bird... It was amazing. Honestly it was the highlight of the game for me, and I still get kind of weepy when I think about it. I think they did an outstanding job with that.

On the opposite end of things, I feel like Q-team was the worst part of the entire game. Dear god every time I had to play as them I wanted to go to sleep. Sean was the most interesting of them by far, and his existence really wasn't actually exciting at all. Mira being a serial killer was completely unsurprising and Eric never redeemed his character throughout the whole game. Again, all 3 characters felt kind of shallow. Eric spoke briefly about his family issues, and I'm not sure if it's because I didn't care for his character, but I felt nothing towards him at all when he spoke about them. Because of this, I had kind of assumed they would be expanded upon later. This might be my issue though, I know that VLR had character specific endings and I may have gotten the idea that ZTD would be more like that than like 999, which had endings that weren't quite that specific. I guess as the last game I really expected the best of both of those worlds, though.

In terms of the true ending, I found it rather disappointing. VLR's true ending left me with a hole because it was set up for a sequel, yet I didn't feel that ZTD filled that hole. I know that it's not in the nature of the Zero Escape games to let you know exactly what happens after the true end, but I really really wanted to know and in the end I felt like VLR never completely got wrapped up for me. With VLR, when I got to the true end I definitely knew it, but with ZTD, after the credits rolled I found myself thinking "Oh, that was the end?" Tbh it's kind of a sucky feeling for a final game of a trilogy.

All in all, I would definitely say that I enjoyed Zero Time Dilemma. As much as Q team sucks, both D team and C team redeemed the game for me and I can't say I didn't stay up WAY too late playing it. I'm really thankful for the Zero Escape games, and they are some of the most fun games I've ever played and I'd recommend everyone (who isn't squeamish) should play them.