Complex sentence: As the Zeon further tested the Gouf Flight Test Type they constantly reworked the design, updating and rebuilding the unit in the field to overcome the problems they were having, but despite the design changes the design was still found to be highly flawed.
Split into simpler sentences: As the Zeon further tested the Gouf Flight Test Type they constantly reworked the design, updating and rebuilding the unit in the field to overcome the problems they were having. But despite the design changes the design was still found to be highly flawed.