Z/X is implemented.
I've soso discovered a memory leak that can occur if too many levels are played during one run of the app (about 90 levels triggers it), I've traced which unit it occurs in but have yet to actually fix it. (Its possible it relates to code I've added since the last update though.)
EDIT: No, it doesn't relate to new code, so be aware of it in existing versions (though it should only happen at the start of or inbetween levels, not during one, so you're unlikely to lose any progress). However, it'll be fixed in the new update.
I've also now added the "save all images" option.