aliens are pointed towards c1 and c4. c2, spy through window.
OR. OR.
c2, throw grenade through window near aliens or at aliens. after firing, c4 enter the room and
get behind cover; c1 stays behind and fires. c2 behind those boxes, try getting the assault rifle. c1, rush for the assault rifle near those boxes unnoticed as their attention might be on everyone else, maybe c4 and c2 can fire while c1 does a flank
somehow.
also use the XCOM suits if possible without their armor, just the slightly better one