I finally had to go back to the vet and complain when I couldn't give my cat oral syringes.

I told them I don't have four hands: two to hold the cat down and one to hold the cat's head, while the other hand is injecting the syringe.

AND I had to worry about the cat taking a swipe at my face.

I said, I see that when I bring the cat in, the ONE vet is able to give the oral syringes, so there must technique to it.
THAT was when he realized he needed to teach me,
the way they are taught in vet school how to hold the cat down. For some reason it doesn't occur to them that just as they were taught, WE have to be taught too.
I used to approach the cat face to face. That is the wrong way to do it. That creates an immediate adversarial exchange.
They said to calmly pet the cat and hold her down while you move around to her butt, or come to her from behind. So the cat's butt is against your stomach or chest, if it's on a table, with the arm not holding they syringe along the side of the cat, where it can feel your arm firmly against it. And your syringe hand along the other side of the cat.
Or, if on the floor, kneel so the cat is between your legs, with it's butt against your crotch. This way, the cat has no where to go. It can't back up and away, and it can't go sideways, either side, to get away. It can only go forward into the waiting syringe moving toward it.
If neither of those work, you may have to drop a blanket over the cat, again from behind, and swoop it over the cat and enclose it, legs and all, cocoon-like in the blanket, with it's head exposed.
Try to open up the side of the mouth, instead of the front. The gums are actually looser along the side. She will be grimacing anyway. You just have to get the syringe against it's side teeth at an angle to shoot the syringe load in toward the throat. Then let the cat go immediately. And apologize profusely, so she knows you aren't trying to torture her with anything else. It's just that damn syringe.
Give it lots of love other times so it doesn't think any time you are coming up from behind she will be grabbed.
Try not to give the dose directly on the 6 hour mark. Cat's have an internal clock and it will start to know when that injection is supposed to come, and will hide.