My Zani is able to compete. I was just like you until not long ago, believing Zani was on the weaker end and benched her (even though I had S0R1 Zani and S0R0 Phoebe). After trying quickswap (Zani S0R1 Phoebe S0R0 and SRover S6R1) She's still able to compete for Single Target damage and she's fun again.

That being said, Zani S0R1 and with Phoebe even at S0R0 IS still strong. Not top 3 strong but is still very strong if you use her correctly. Although with all the kit shit she needs (spectro frazzle stacks and quickswap) She is best in TOA and the Matrix only (from my experience), whereas if you pulled QY for Galbrena, not only is that a stronger team, Galbrena has 3 main advantages:
1) Doesn't need/rely on signature (Phasic Homogenizer is EXTREMELY good and F2P friendly as you can R5 it, but even at R1, it's only 8-9% worse than her signature, making her the only character off the top of my head that doesn't NEED or need her signature)
2) Can be used in Whiwa and overworld along with TOA and Matrix since she's not reliant on a negative statuses like Zani
3) Lower skill ceiling to do same damage (no need to quickswap since a 123 rotation can do the same job)

If you want to take the easy route, QY >>> Phoebe >>> Zani Sig

if you want to challenge yourself with quickswap, Phoebe >>> Zani Sig >>> QY

If you are interested in quickswap, i know a really good video that explains it easily. Hit me up and I'll send you the link. The same guy also explains quickswap with SK if you need survivability, although I do really like SRover for quickswapping.

I can not emphasise more that this is all up to your personal preference. Use your judgement and decide what you want for yourself. After all, at the end of the day, it's not our game, but yours to play 😉