Does there exist hardware/software that allows guitar to play synth sounds with zero latency?
You can’t have zero latency because you have to watch the string vibrate for a bit to figure out what its frequency is. However, the latency is quite manageable (IMHO) with systems like a GM-800 (I have one):
Their two products are BOSS - GM-800 | Guitar Synthesizer and BOSS - VG-800 | V-Guitar Processor
There were some systems that might have been faster (that could tell both the string and the fret), but those have been abandoned from what I can tell.
There is at least one all-software system, but I’ve never tried it, but it might be worth your consideration:
The EHX pedals, synth9 etc are pretty sharp
I remember trying some Boss guitar synthesizer stuff years ago - the latency was decent but the sounds were uninspiring.
I suppose I’m more interested in controlling string and wind instrument plugins in my DAW with the guitar - I think there is a controller that you blow into and bite with your mouth that helps this but I need to do more research.
Ah actually I think I did see some youtube vids in the past regarding EHX synth pedals that I was impressed by.
It sends MIDI events, so just connect it to the synthesizer of your choice.