Lurker is VERY hard to beat at my level. Plat2. I try to fight them with imortal, colos, archon, stalk, charglots. Occasionally I can beat them, IF my detection doesn’t get sniped. By more often than not they just eat my army.
Zerg usually has hydra supporting them.
So unless I quickly tech switch to air, I’m pretty much dead.
I’m a zerg player, so feel free to correct me here. I find my lurkers can struggle against disruptor, especially before quick burrow - I cant clump them anymore and spreading them is extra micro I need to do, which might give you an advantage if I start lapsing my macro. Disruptors also zone out and devastate hydra/ling numbers. They should at least buy you more time to make a protoss deathball.
You could also make a few phoenixes, maybe 2-4, to lift and kill lone lurkers looking to do econ damage or ones rallying across. No need to commit to tech switch into air for phoenixes
Something cheeky I could see, but probably isn’t reliable, is using DT’s and sniping any detection they bring with them. Psionic Storm also deals well with them, if you can get in range - don’t even need detection.
Just send/drop/warp 5 chargelots simultaneously in each of his bases. He will either lose them all, or start running home with his units, allowing you to kill the lurkers for free with your main army 
For Hydra/Lurker army, what I find the best is a Carrier/HT army. Carriers wreck Lurkers and HTS wreck hydra, so its an Interesting dynamic. If he makes a lot of Lurkers, he usually doesnt have enough Hydras for the Carriers. Make too many Hydras, and HTs rip em apart.
Having Oracles still alive from the early game helps with revelation.
No simple counter though as far as I know. If it’s too early and you can’t get enough Carriers for this Carrier/HT army, disruptors might work.
Personally with my standard zealot-archon- immortal army I try to rotate all the time and stage at least one run bye apart from the main army. You cant see it but the zerg must all the time then unbaroow and reburrow the lurkers, move the rest of the army. Then at our level (Diamond 3 here) big chances are you will catch at least part of his lurkers unbarowed, then you can pounce and kill him… OR the runbyes might do good dmg. The worst thing you can do is attack froom one side into burrowed lurkers with rest of his army on top… IF he sieges your base with 6+ lurkers and some hydras /ravagers, its very hard to win with standard ground army, you cant rotate then as you defend.
My zelot run bys are decent. But some zergs make lime 5 spines at the outer bases and it kind of nerfs them. I’ve been switching straight to air against zerg now. Winning about 50%, if I can get a good carrier count before they all in.
Nice, whatever works for you:)
Lurkers are very hard to deal with particularly when supported by hydras.
Here are some tips:
Harstem made a video about it.
Try to play with a few colossus, single uses of templar (meaning don’t use them as a blob but single them out to prevent lurkerhits on the group) and go into max of 6 carriers when getting close to max.
Try to hit lurkers with templar when they are burried and force constant repositioning.
Try to prevent playing with archons and if you see he has lurkers, try out constant pressure on the outer expansions or his natural (most of the time no spines there) since lurker armies tend to be deathbally, meaning bad to split up properly without over or undercommitting at one particular side.
You can abuse that pretty badly.
add Disruptors to your composition
You dont even need the Observer if you have Disruptors…
Disruptors, Stroms, Immoralts in high numbers, Any skytoss units.