Not sure about Zyprexa but I've had small amounts of benzos completely kill trips before. I know a lot of people insist that this doesn't work, but it definitely does on some level.
Benzos are a good first line of defense should something go wrong, and im all for working through the problems that are presented to you on a trip, but the way I see it, benzos are just central nervous system depressants. Its gonna slow everything down, including the trip to some degree. This i believe is what you are experiencing, but i think this "level" you are describing is very shallow. Unless the benzo knocks you out (please dont take this much), your brain is still functioning and then therefore reacting to other drug in your system, LSD.
Antipsychotics like zyprexa, as indole said, bind to the receptor sites (both the 5ht2a and dopamine sites) that LSD agonizes. Zyprexa effectively plays goaly at the receptor sites that lsd is trying to score at. This feature, combined with the sedation caused by zyprexa (wikipedia says this is due to its action at histamine sites), makes zyprexa much more viable as a trip killer.
The catch is that when antipsychotics are used to treat actual mental disorders, it takes around 3 days to take effect. I dont know if this is the time it takes for the personality to catch up with the changes in neurochemistry (if this is the case taking zyprexa should kill a trip), or if 3 days is what it takes for levels to build up so that they are effective in changing the neurochemistry (if this is the case then antipsychotics shouldn't kill a trip). Seeing as there have been reports of antipsychotics working (including a report of my own), if say its safe to say the former option I suggested is corret.
PS if someone that actually knows something about neurochemistry could correct me I would be greatly pleased.