Eway Bill

we are dealing in solar water pumping system. if suppose we received order from government department for supply , installation & commissioning of solar water pumping system to to different places . we have to send material part part by for installation purpose in that some material is of 18% , 12%& 5% . firstly we have to send module mounting structure which comes under 18% slab, then solar pump , panel & assesories . after the completion system is installed . we have raise invoice to the department which hsn code is 85, which comes under 5% slab. so how we have generate eway bill part part material send to sites