The key factors for Zerg are:
Zerg nuke defense can either b extremely easy or extremely hard. It can be easy if someone is nuking you without medics. Or it can be hard if someone is using more than 2 medics blinding all your overlords.
Overlords- Since you always have an abundunce of overlords its not very difficult to mass these. Therefore simple to find ghosts, however if they have more than 2 medics you may find yourself with 6-7 blinded overlords. This is very bad against terran reasons bieng 1.) You won't be able to find ghosts 2.) If they come in with wraiths your going to be screwed over. So if your going ghost hunting bring all your ovs if u can
Ensnare- Get a few queens and if you can reveal a ghost just long enough to find him b4 your overlord is blinded you can ensnare him revealing his position with this green crap. Then just rush in with units. This works the same with plague, but its really a waste of plague. The best thing to do if you have the visibility is to just use broodling on him, its fast and simple but this is a condition only if your overlord isn't blind.
Parasite- Same with queens but this isn't as effective as ensnare or plague since it can just b restored. But most terran players don't research restore so you more than likely have the upperhand. What you do is go in and parasite ghosts, science vessels, dropships, medics whatever you c that may come with the ghost.
Spore Colonies- These are the same as terran missile turrets but they suck even more. The reasons the suck even more is because of the zergs restricting creep that forces you to place buildings on it. I'd recommend just sticking with overlords and queens. But make sure u still get some of these for air defense.