Yes, it was explained in another thread that Yordles are advanced with magic, but with this new Ask Riot article, it seems like Yordles are the furthest along with vehicles. Most nations are just now getting into gunpowder and hextech. Yordles are able to pilot planes and mechs.
well im pretty sure they live in little huts in stuff if i remember, humans seem like the overall most advanace race considering that piltover and zaun are mostly comprised of humans, 
Perhaps advanced isn't the right word, but inventive and ingenious. Yordles seemingly make wonders of their own devising for the hell of it and keep trying until it works. Because their works aren't as limited by physical construction due to magical influence on their part they can make all manner of strange things. I'd imagine that yordles have all manner of weird and wacky things lying about their homes, not necessarily all technological, but all of it enchanted and wonderful in their own ways. There's no scientific drive, it's just yordles doing their thing. It could be that yordle ingenuity inspired humans to try and pursue that kind of progress, leading to great advancements in technology as a result.
Kinda wondering if Heimerdinger might've had a role to play. Maybe.
Meglings were the most advanced race before the genocide.
Pretty sure 
is the most advanced. On a more serious note, Zac was invented by Zaun, meaning they must have some major brainpower.
Rumble Corki Heimerdinger
If we are talking technology, I'd say they are on par with Zaun/Piltover. Actualy, Heimerdinger is an hextech master and works with Jayce, so Piltover and Bandle city are probably exchanging thechnological knowledge. Yordles are great at building vehicles, mechs, robots, etc.
However, Piltover is probably the most advanced city in terms of architecture. http://vignette3.wikia.nocookie.net/leagueoflegends/images/a/a4/Piltover.png/revision/latest?cb=20150720113202&path-prefix=fr
Here is a comparison of Piltover and Bandle City.
As for Zaun, they are advanced in the revival of dead peoples 
and good in robotics too. They also are the only one confirmed to be great in chemistry 
and some even developped serums to change forms 
To compare the technologies, we can also take a look at champions from the 3 scientific nations
Piltover:
Nothing much technologic about her, but her gun can change form depending if she is just fighting of if she is snipping (her ult)
Lore kinda outdated, but he developped some kind of technology that works well with his magical abilities and he is said to be very smart. His gauntlet can channel his magical power, so we can say Piltover has some kind of knowledge in magic.
Probably the most advanced robot known to date, she has a mind of her own, tries to understand things and does what she pleases.
His cannon works with the energy of ancient magical crystals, just like every hextech technology. He also seem sto have a kind of vest that helps his physical capacities (no normal human can just do a double front flip with a hammer that big and slamm it on the ground than keep walking like nothing happened)
Her gauntlet were made by herself and then enhanced in piltover. They are shown to be easy to wear despite their huge size and can propel her forward when she wants to. She can stock power in them to empower her punches. They are probably hextech too.
So basicaly, Piltover seems to have a lot of mechanical knowledge. Weapons that swap form, crystal powered engines, robotic, weapons...
Zaun:
One of the most advanced robots made, he is said to work with magic and steam power. Can move on his own and speak, he also has a mind of his own. I still think Orianna is more advanced since she tries to understand and evolve as a human, looks more fluent than him and she can control another entity (the ball) while blitz only does simple commands (walk, walk faster, grab, punch, discharge)
these 2 bitches enhanced their physical abilities with some kind of serum or whatever. So we can assume they have great biological knowledge and know a lot about chemistry too.
A kiddo from the street that somehow managed to make a machine that can turn back time itself. Probably some complicated physic things, or just some magical stuff since Zaun is also known for its dark magics.
One of the best chemists in the world, can create deadly poisons, chemical weapons, enhancing serums and stuff like that.
Both brought back to life with the help of Zaun tech and Noxus necromancy. I think Zaun even have a place for revival technologies researches.
Has been able to replace almost every part of his body by robot parts and also worked on blitzcrank, so than again great robotic knowledge.
Litteraly a living goo, this imply great biology and chemistry knowledge again. They have been able to create an entity that lives, think and acts with his own mind and even developped a personality, thats some heavy stuff right there.
Bandle City
His plane was made by heimerdinger, althought its a pretty basic one its the only plane known in league, so yordles are the only one known to have airplane craft.
One of the greatest scientists of the continent, all of his spells are made of his enventions, he can stock turrets in floating thingies around him, has electric grenades, missile launcher in his hairs, fancy gogles and bronze can't lane against him.
Nothing very scientific about em bitchez. Important to note that Veigar tried to steal the ''mothership'' tho. Never saw it but its probably some kind of space ship so again yordles vehicles are more advanced than others.
has a mech. Just like Corki it seems pretty basic but hey he is the only one with a mec in this game.
Got his gogles from heimer
SO BASICALY:
Yordles: More advanced in vehicles and gogles
Piltover: More advanced in mechanics/Robotics (we could compare Orianna to Viktor, but Orianna can have a mind of her own and live as a robot while Viktor needed to keep some of his human parts to be able to function) and can make some pretty dope weapons. Probably the most advanced in hextech since Jayce created it but they share some knowledge with the Yordles.
Zaun: More advanced in term of biology, revival and chemistry. Also has some time tech we don't know a lot about.
If we are talking magic, i'd say every civilization has their own specialities, but all Yordles are known to be able to use magic while for humans only some people are gifted with it.
I guess it depends on where they live. Yordles close to zaun or piltover probably feat far more advanced technology than any others.
I mean, look at Kled.
Probably they are so dispersed now that they are unable to share their technology with their kin, and if they do then it' s very rare. By the looks of what Riot gave us, Yordles once they leave their magic realm or show themselves to humans can' t go back anymore or if they do they have some kind of problem or unwillingness.
Heimer and Rumble were the ones who built the Mecha skins (in an alternate universe) so Yordles are more advanced
