B & G Dou - Flo Valve??? Main loop Supply/ Return and Secondary loop Supply / Return

My question is what can I use in replacement of this valve and how to pipe it .. I'm sure I'm over thinking it as well … I have called B & G / Xylem spoke with local reps and no-one knows what it is or what it does … There is 4 zones all have their own valve identical to this one Main supply goes into this and out to the main return loop while in the center of this is the units zone loop supply/return. The red Bell looking things are the valves , now i dont know if they are for balancing or are for isolation. or both. my problem is this unit is getting hottttt!! replaced the thermostat it is functioning properly. The pump is with-in a year old. I even pulled the circ check valve to make sure it was working properly. so the only thing i could think that's faulty is this B & G valve. Please any assistance would be great. Im sure ill be replacing all of them sooner than later there is 8 zones per floor 14 floors .