How to deal with Planetary Fortress with Turrets as Zerg

I'm a platinum player Zerg and I have one huge problem with ZvT. If a terran manages to sneak expand somewhere on the map and build a planetary fortress and surround it with turrets, it's very hard to react. Even more so if the expansion is in another main with a ramp/choke.

A PF with repairing SCV:s can withstand a ridiculous amounts zerglings/rouaches and same against mutas if turret repairing is done right.

Then the terran can just rest with his tank army and as soon as you try to take the PF down by brute force, he kills your main/natural.

The only ways I can deal with this is to go Broodlords or out expand my opponent, but it feels like there must be a better reaction to this.

Anyone has any clever ideas to deal with such situations?

The only other and usually more surprising method to take down a planetary fortress is to use banelings.

It takes 20+ banelings to blow it up. A few less if you have upgrades, but you can never have too many banelings against terran.

You'll need to produce a few extra or just lead in with a few zerglings to take the first few planetary fortress shots until your banelings can connect. If you're lucky you'll be able to blow up a few SCVs as well.

Keep in mind this is somewhat cost inefficient, but come mid/late game you'll be able to afford to do this and sniping off an expansion in this manner is very effective if they're only down to a few mining bases.

Planetary fortresses can actually be a good thing to come up against depending on how you look at the situation.

The natural response for most players when their undefended expansion comes under attack is to withdraw their workers, and sacrificing only the cost of the town hall. The Terran player with the planetary fortress' first reaction however, is to simply repair the town hall instead. So just move your zerglings into the worker line, hold position and watch their SCVs get torn apart. Use a roach ball to tank the planetary fortress while your zerglings are doing this.

Now you have two options. Withdraw your army and let the planetary fortress do nothing (since you destroyed all the workers) or overwhelm it with zergling/roach/hydras since it is no longer can be repaired.

Banelings can be helpful, but the planetary fortress will target them first automatically before they can get in range of the SCVs, so you will need a lot of them.

The most common solution is to go muta. The muta's attack bounces three times, doing damage as it does so. If they mass-repair, then the glaives will kill the scv's pretty quickly.

If you really want to go ground units, ultras are probably your best bet. The splash damage allows them to tear light units to shreds and they do +20 damage to armored.