Hello!
If you like your Oyster Zero, I would absolutely not hesitate to make it a pram/stroller system from birth, because YES, you can make that from the pushchair version. There are actual adapters, and a carrycot (the same as for the Oyster 3), and the good news is also the fact that wit those adapters, the carrycot part will be higher up on the chassis, perfect for taller parents.
Truth to be told, if you're really happy with it, I wouldn't really look for something else - the 'carrycot-only' prams are quite limited to choose from. Either they're quite low to the ground (like the Mutsy brand or the Cam Dinamico Up), or very retro-styled with fixed wheels and all that - including nice suspension, but that also means they're quite bulky, or they are very very expensive for a pram-only (like the Stokke sets or a Gesslein Indy...).
Another option you could go for are the 2in1 pram convertible to a seat, which are very useful for those first after-carrycot months when you want to see your baby, and after you can pass on to a forward-facing-only pushchair for toddlers. If you already own the Oyster Zero, that's actually a perfect combination. I would suggest a Diono Quantum or a Maclaren Daytripper. They're not the 'tallest' of prams, but the nice price-performance ratio is balancing that out, and if they feature an adjustable handlebar, there's not much to think about...