Easter Sunday is the first Sunday after the first full moon after the vernal equinox.
So it varies from year to year, nothing to do with Hey Zoos!
Well it obviously is to do with "Hey Zoos" as otherwise it would just be the first Sunday after the first full moon after the vernal equinox wouldn't it? And shrove Tuesday (iirc) is to do with eating all the "nice" stuff before the 40 days/nights of Lent which represents when "Hey Zoos" was in the wilderness.
Or something. But it's definitely to do with Jesus.