Always inherent to a type of engines to equip a future heavy destroyer with a displacement of 6000 tons
To avoid future surprises the best choice is to make the motors in Iran, either with a foreign license or an Iranian patent
The ideal would be a CODOG system, with diesel for economic speed and gas turbines for maximum speeds, all on two axles and relative propellers.
O CODLAD COmbined Diesel-eLectric And Diesel
However, it will not be easy to find or build gas turbines for naval uses, and CODLAD is also not easy to build.
So you could (I hope you don't throw stones at me) opt for a CODAD system like on the Sahand 74, with diesel engines of about 5000 hp each (preferably made in Iran), but to reach a speed approaching 30 knots not 4 engines are sufficient, therefore, considering the dimensions and spaces that the new destroyer will have, one could opt to double the number of engines (8) which would thus provide about 40000 hp of power, each pair of engines connected to its own gearbox on one of the 4 propeller shafts.
Certainly not easy to build and with a more elaborate hull to accommodate 4 axles and related propellers, however it could be a solution, provided that as written above, motors and gearboxes are made in Iran.
PS
just to play with the images