I thru-hiked in 09. I had a Houdini and a rain jacket and would bring both again. Getting sweaty under your rain jacket sucks, and the Houdini is amazingly breathable--I wore mine all the time on the trail. Also, if it's really cold (which it will be at some point), you can wear the houdini under the rain jacket for a bit of extra warmth.
I would ditch the zip-t (use your houdini/rain jacket for extra warmth during the day; sleep in your down jacket if necessary). I'd also ditch the long underwear top for the same reasons.
On the PCT, I never hiked in anything other than my base layer, Houdini, and rain jacket. I had one extra t-shirt for town/sleeping and an insulated jacket. For the Sierras, I added a mid-weight poly shirt for sleeping, but I had a pretty light sleeping bag and needed the extra warmth. If your sleeping bag is rated to 20 or lower, you probably won't need a lot of warm clothes to sleep in.