I applied silicon lubricant in liquid form, very small amount, during the very cold spell. I was at the boat last week, and zips were better than when I bought the boat. Wikes sell it as lubricant for pushfit underground waste pipes, probably 50yrs supply.
Bees wax or plain old fashioned candle wax (I simply ran a candle over the zip teeth) always worked on my heavy duty dry suit zip - can't see why it wouldn't work on canopy zips. Less messy than vaseline too.
Silicon lubricant is the best. Use it on the zips and poppers and no problems for the year. Candle wax is also good. Burn the candle and then let it drip in to actual zip body and its then loaded evey time you use it, Just dont burn the canvas.
Watched someone use vaseline once. What a mess after a couple of days
Don't use oil or vaseline, dirt sticks to anything greasy and will cause more harm than good. WD-40 type oil is bad for adjacent fabric and may start rot etc. Bees or candlewax works ok but looks messy and needs regular and more frequent application.
I was looking for a silicone aerosol a couple of years ago and found a tube of silicone grease labelled, 'Zip and fastener' lubricant. Works extremely well and you need very little of it.