when you face m2m its tricky to know what to change. often it makes sense to up the distro of the guys with favorable matchups by 1, maybe 2, and to lower against the top defenders. it can sometimes make sense to change your lineup, but that is a much more complex decision. you have to weigh the natural value of having the 2 players at the positions they currently play, against the increased offense. so for example, if you have a true pg with 80bh and 90 passing, and your sg is 70 bh and 60 passing, you are most likely never going to switch the two. but if you have two bigs who are similar in terms of ath/def/sb/reb, and one can score well, you may switch them around purely based on the opposing team (when playing a m2m defense).
but anyway, in your situation, a big part of your struggles is that you are new to d1 and still need to get the hang of recruiting. its tough at a d+, i did really poorly at my first d1 job recruiting wise, but you'll get it eventually. with zone you can afford to take a shot at some better players and risk taking walkons, you pretty much have to be doing that to justify running zone... you want to at least start setting a minimum threshold, only sign players you'd kill for in d2. you have massive advantages recruiting wise over a+ d2 schools, so you should at least be able to set that as a good minimum starting point.