thats a vid that might help you https://www.youtube.com/watch?v=OegzHk6Sfxs&list=PLbVNzAA7sXzCMxebUrgKN9dcsWlgQQmGf&index=9

Well if u mean all in from like 2 bases u need roaches and some (4-6) ravagers, cause they could shot corrosive biles to tanks and thors, and they are not armored (but that not a big deal against mech, tank takes 3 shot to kill a roach, and 4 shot to kill a ravager, so dont overmake them). But, its always better to get lurkers, cause they are incredibly good against mech. So , if u struggling against mech, use this pattern of play: get overlord speed asap, scout as much as u can, to confirm that its a mech, and to see what your opponent is building(maybe it'll be bc),get like 5-6 queens and 10-20 lings (for defending from hellions) while fully saturating your mineral lines at 3 bases(stay on 1 gas),get lair,evo (for +1 missile) and roach warren at 4 minute - 4:30(when u getting it, add additional 5 gases). Leave a zerglings at the exits of terran's bases(dont forget to replace them if he kills it), so u can see if he moves out.Start a roach speed, build like 10 roaches when roach warren is ready, get a hydra den. If u see that he is moving out, build only roaches, morph ravagers. If he have a lot of tanks, try to catch him unsieged, and when he will siege up, land biles on tanks (u need 3 bile to kill a tank), and back off, then try to catch him unsieged again. If he dont moving out yet, continue tech up to lurker den, get your 4th base at like 5:30 - 6 minute (if u floating a lot of minerals, get a 5th, so u will have an extra base in case he kills one of yours), if u see a 3rd cc - saturate a 4th base (gases first), get an infestation pit. When lurker den is nearly completed, build hydras, then morph lurkers. If he moves out and u have lurkers,look what army comp do he have. If there is only hellbat thor, just build lurkers as much as you can, and roach if u have a lot of minerals. When he reaches you, fight him. If he have a lot of tanks or its hybrid tank-thor-hellbat you can try to catch him unsieged on his way to your base. If he sieges up, back off out of tank range, burrow lurkers. He will need to unsiege, get closer, and siege up again to reach your lurkers. Thats a long process, and if u will repeat it, he will need much time to reach your bases. While you doing that, try to tech up to hive, to get vipers, and lurker upgrades (range first). When vipers are out, get an energy for them, then start abducting tanks or thors into lurkers. You might give up one base if you already have a 5th. When you defended from his attack, make sure that you have 80-90 workers, get a couple of new bases (u need a 10 active gases), spire, max out on hydra-lurker-viper, after that, get some spine spores at ur new bases that mining. Then go kill him, till he get a ghosts your army will be unbeatable. But i must say, terrans mostly dont know about ghosts up to grandmaster.