I have been tired of the Peg choices for ATK's (ZERO) for years and so modified mine to take another brands. I used the mounts for a XR100 as there is a wide varity of pegs for this out there. First you need to source the mounts and the Pegs you are planning to use. I have Fastways on one and Pivot Pegs on another. The mounts can be had on e-bay for as cheap as 10.00 a set or new with the PN's below:
PN 50615-GN1-000ZB $14.96
PN 50624-GN1-000ZB $20.82
You will need to remove the u-shaped part the peg mounts to.
Thats the cut bracket sitting in front of the peg post.
Use a camber/angle gauge (4.99 from Sears item# 00939830000) to find the angle of your stock pegs (up/down and front/back) then remove the stock peg and cut the stock mount at the rear of the pin hole.
Then mount you chosen pegs to the cutoff u-brackets and tack weled them at the stock angle.
You can even move them around a little to suit your leg length and riding style. Get on and check that you are happy with the position then finish the welding. This is not a job you can skimp on the welding so farm it out if needed, you don't want a mount breaking in the middle of nowhere.