Diesel-hydraulic refers to a hybrid system that utilizes the power of both diesel engines and hydraulic systems. If you're looking for synonyms for this term, you can use the phrase "combustion-hydraulic" to describe a similar mechanism. Another option is "diesel-hydrostatic," which also refers to a system combining diesel engines and hydraulics, but with a different emphasis on energy transmission. "Diesel-electric" may also work as a synonym, describing a similar hybrid system that replaces the hydraulic part with electric power. No matter which term you choose, each refers to a method of combining diesel engines and other power sources to create a more efficient, high-powered system for heavy machinery and transportation.