cupla problems with Tascam stuff (I don't know if they have fixed it with the mark III)
If you are taking a stereo mix in 2 channels, they will become phase-inverted and when you go to mix it, you will get a nice sounding WAV with both sides being 180° out of phase. If you listen to it in headphones on the tascam, take the stereo mix and roll the pans up to dead center. If the volume drops drastically, you got a problem (unfixable) with the print.
If your mixer does not have a reverse-phase switch for the output then you need to take an RCA cord, cut it in half and switch the polarity. Use that for the right send to the tascam from the board effects send (I don't know how many sends you are talking about here, 2?) That will fix this problem.
(ah I see you weere talking about a mono send from one effects send)
Depending on what you are doing, if you are putting stereo music on 1,2 and individual vocals on 3,4 then use the zoom box for mixdown. Otherwise use it on the samson during recording.
For what you are describing though, send effect 1 without effect to the tascam, and just use effect 2 for the effect. I imagine you are going to put out live mikes? You might be able to get a good mix with 1 line out from the board and 3 external mikes.