That’s a good idea to let the oil jugs warm in the sun.While I was changing the filters and doing the engine oil change, I left the jugs of hydro fluid in direct sunlight, shaking them a couple times to help distribute the heat. After opening the vent port on top of the hydro, it took less than 10 min per side to fill.
I have ZT3100s and it’s definitely tight to get a ratchet and socket in there to remove the vent plug; I found the S-shaped wrenches make it much easier for both angle of access and vertical clearance.