It depends, but yes some Ikelite housings can be modified to zoom.
Generally, it's not necessary:
It's possible, but composition through a viewfinder or even live view is hard. A mask is limiting, lighting is harsh, and live view eats up battery life. Most u/w DSLR rigs benefit from wife angle lenses so photographers don't miss a shot. Cropping often yields better results than zooming.
Water quality is often poor. Folks complain about low light photography on land. Underwater is magnitudes more challenging as you're literally working with a reduced color spectrum; fast light absorption and luminosity decay with distance; silt and sediment obfuscating a shot; and backscatter ruining and worth with a flash. Shooting at a distance is just plain hard, so shooting as wide as possible is usually your best bet
Underwater, there's an apparent magnification of around 33% so increasing focal length to enlarge a subject is already kind of covered, at least to some degree.
Adding holes obsessed the chances of failure and a total loss of equipment. Unless it's really necessary, it's wise to avoid
Ikelite housings are already expensive af. This is another wormhole
Buuuut it is possible. These let you zoom but I wouldn't really submerge that completely. That's more of an emergency rain/splash protector than an underwater housing. So it depends I what your needs and requirements are. Holler if you want to provide some more info like a budget, etc.