Given most people don't have muzzles for their yorkies....BUT if you do have a muzzle I have found that putting the muzzle on and putting the syringe on the side of the mouth like you would if you had a helper works fairly well. And then I take it off after she has licked up what she could spit out just by trying to get more of it out she licks it.
And give her lots of treats.
I don't have a muzzle that fits my smaller one and she just had surgery so we were going through the meds thing and mostly it was fighting trying to convince her I was calm and to be calm. That is also a helper, if you can stay calm. My girls can definitely feel my nervous energy and they get nervous, so even if I am nervous about doing thing for them I do my best to stay calm (ie. meds, nail clipping, brushing teeth, etc)
I also found if you squirt it all at once it is better than a little at a time. With a mouth full Somi was much more inclined to have to swallow than with little bits she could spit it out.
Good luck with giving your meds.