Complex sentence: At the same time, the La-7L waqs tested with a new laminar flow wing by TsAGI, and another La-7 was tested with the new Shvetsov ASh-83 motor.
Split into simpler sentences: At the same time, TsAGI was testing a La-7L with a new laminar flow wing. Finally, another La-7 was tested with the new Shvetsov ASh-83 motor.