Props to Peter Chen for the email and RandomShadow09 for this:
It would appear that the Sidestrike holster will not be able to hold the Zombie Strike Hammer Shot which is a bummer to be honest. Guess ever more reason to pick up a Nerf Rebelle Sweet Revenge.
Nerf Zombie Strike Sidestrike Blaster
The ZOMBIE STRIKE SIDESTRIKE blaster is the first NERF blaster with a holster for both dart and blaster storage, leaving hands free to carry supplies and post-apocalyptic gear. The quick-draw blaster possesses ELITE performance, firing ZOMBIE STRIKE darts up to 75 feet. The included holster is also compatible with the NERF FIRESTRIKE blaster, sold separately. Comes with six ZOMBIE STRIKE darts. ($14.99)
NERF ZOMBIE STRIKE HAMMERSHOT Blaster(HASBRO/Ages 8 years & up/Approx. Retail Price: $15.99/Available: August 1, 2013)
One way to survive the zombie apocalypse: Keep moving. The compact ZOMBIE STRIKE HAMMERSHOT blaster is designed for defeating the living dead on the run! Featuring a five dart, front loading rotating barrel and a unique pull-back hammer mechanism, the HAMMERSHOT blaster is the go-to for sudden zombie attacks. Includes five NERF ZOMBIE STRIKE darts. Available exclusively at Target.
The designs are inherently different I'm not convinced that they will fit together. There are mixed feelings about this from the Nerf community but I'm more inclined to get off the fence and say it won't work.
I will however reserve judgement on the compatibility with the Rebelle Sweet Revenge (previously known as Wildshot which I thought was much better).
With some minor cosmetic changes (Hammer Shot under barrel chopping off), it could make a snug fit.
If you know of any alternative suitable holsters let us know!