Combining single cell LIPO chargers into a multi-cell charger
Yes potentially it will work, but 
it will not work if both USB power inputs are connected together

if you use individual AC to USB adapters ("phone chargers" or similar) it will work,  but if you try to connect both Li-poly chargers to the same USB supply you'll have gnd on both Li-poly chargers connected together. if you follow the lines you'll see that that would short-circuit cell2.