You might try protecting them in winter and during early fall cold spells and spring freezes. SInce most Hydrangea macrophylla flower on the previous year's wood the buds can be damaged by cold weather before they get a chance to flower. There are some macrophylla types that will flower on the current year's wood but we don't know which ones you have.
You asked about pruning, trimming and fertilizing. Is that to try and get flowers, or are they too big for their location? For flowering you need to leave them pretty much alone except for removing dead branches, and in your zone they may benefit from winter protection.
