Lambda's usually like to throw out parsers after 5D(if they are fishing for CH and they -think- they got one). Sometimes after 5DD or 4DD (they are spamming hoping you try to jump away and catch you with it). You have to remember that zwei is air unblockable, so if the Lambda is expecting you to jump, he will probably throw it.
The other parsers they like to do them after close ranged attacks like 5cxn, 3c, 6c. They will sometimes attempt a A version for a throw, B version for going low, and randomly C version to attempt to catch a jumping opponent.
Really though, that's just something that depends on the Lambda player a lot and it's something you personally have to watch out for, hell, some lambdas just randomly SPAM zwei. Oh yeah, some will do 214D(~C) then if you blocked it, they'll do zwei to try to remove another Primer, or after 236D as well. Watch the Lambda's habits and know when they seem to enjoy throwing out those act parsers, then punish accordingly.
This is just some input from a half-time Lambda player though~ And, I don't personally feel like I have THAT much experience with her. But, hopefully it's enough information to sort of give you an idea of habits I've seen intermediate Lambda players make. The better Lambdas will rarely throw zwei unless they know a jump is coming or if it will hit. :s