There isn't a best zero distance for HFT. It should be chosen in conjunction with the scope height and pellet trajectory and to some extent the mag and reticle you have to make the targets you have the most difficulty with as easy as possible.
Just slap a scope on and shoot for a while to determine where your range finding strengths and weaknesses lie then choose a setup that helps you where you need the most help.
A very low scope and 20-25y zero will give you one aimpoint through all the 15mm kills but a steeply dropping pellet at longer range which spaces out the far aimpoints and requires good long distance range judgement.
If you have difficulty with the longer distances then a very high scope could give you a single aimpoint from 35-45y, well one that will be in all the kills that can be placed at those distances but your range judgement for the 15mm kills will need to be very accurate within +/- 1y on the closer ones to ensure you knock them over.
The actual zero distance doesn't really matter as long as you know the aimpoint for each distance, choosing one that falls on a round number and close to your px setting will ensure checking it is both easy and accurate.
2 setups both zero'd at 25y could have as much as half a mildot difference at 45y and several dots difference at 8y depending on scope mag and mount height.
So asking what is the best zero distance is a bit like asking what size shirt is best
My current setup is on a 15y zero