Complex sentence: The ISU-122 was used as a powerful assault gun, a self-propelled howitzer, and a long-range tank destroyer, the same as with the SU-152 and ISU-152 heavy self-propelled guns in general.
Split into simpler sentences: The ISU-122 was used as a powerful assault gun, a self-propelled howitzer, and a long-range tank destroyer. This usage was the same as with the SU-152 and ISU-152 heavy self-propelled guns in general.