I've won plenty of games as taric. Used to and still do some times wreck lanes with all ins at level 3 and 6. Your still not swinging me. Zyra offers nothing to her adc, in fact she's even more reliant on her adc, than leona or taric. Sona is the most easily bursted supp in the league. I think she's strong, but make one mistake in your positioning and your dead.
Loads of other people have explained how Zyra works, but more about Taric. Of course it's possible to win games with Taric, but he's a passive sustain laner for the most part, and you're not going to get kills in an all in without your adc.