One of the largest, and to my mind best, garden centers in the ZH area is Meier in Dürnten:
https://www.meier-ag.ch
It's well worth the trip - even if you are only shopping for ideas. Excellent selection - but not inexpensive.
ETA: Meier has a customer loyalty card that gets you IIRC 5% off your purchase, a nice deal. And their (gratis) monthly newsletter is full of tips for plant care, worth signing up for.
Also, Haeberli Beeren is a producer of all sorts of fruit, trees included, excellent quality. You can buy directly from them at their place in Neukirch-Egnach, or from any of the retailers carrying their lines. Meier carries their trees and plants, by the way. Their website is a treasure trove of info, worth reading through as you think about what you might want to plant.
https://www.haeberli-beeren.ch/de/wo...irektverkauf-2
As for regulations:
Yep, rules abound. These are generally both cantonal and local.
Additionally, you have to deal with neighbors' sensibilities - and do not underestimate how much Nachbarstreit is fueled by hatred of trees. I've never understood this attitude, but it's fairly common 'round these parts. Take paradise and put up a concrete box. In a country where the amount of sun and view of XYZ can add squillions to house prices, many see trees that give shade or privacy as negatives. There be dragons, tread carefully.
Generally speaking, there are rules for how far from your property boundaries you can plant a tree, as well as rules for the height a tree must be kept trimmed to. There are rules governing if a tree branch hangs over onto your neighbor's property, if the leaves or fruit fall into his garden, if the root system encroaches his land. To avoid sparking Tree Wars, you need to understand these regs when you choose what species to plant.
As a start, see this article with a link to the various cantonal regs. For ZH, see art 169-174 in the link given at the end of the article:
https://www.beobachter.ch/nachbarn/n...-und-straucher
ETA:
Here's another site collating the various cantonal regs:
http://www.pflanzen-im-nachbarrecht.ch
When in doubt, ask the good folks at your Gemeinde what the specific local regs might be.
There is also usually a Frist, a period where a neighbor can object to a tree. It's five years in my area. Once you plant, your neighbor then has five years to make a complaint. One of the games played around here is to wait to object until just before that Frist expires - so you have the heartache of having to chop down a beautiful tree that you have nurtured for so long.
Additionally, some neighborhoods will have further restrictions either by covenant or informal agreement. Sometimes you have to get your neighbor's permission to plant a tree.
Or not.
As with absolutely everything in Switzerland, YMMV. You might have delightful, reasonable, live-and-let-live tree loving neighbors who are happy to see you doing your bit to promote a healthy environment. If so, count your blessings and enjoy your gardening.
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A tip:
Knowing my neighbors I tried to play it safe and plant dwarf versions of fruit trees. But I made a mistake:
Having grown up hearing 'You've got to dig a ten dollar hole for a two dollar tree', I did just that. But apparently if you plant a dwarf tree too deep you run the risk of it reverting to basic type - which mine did. Several of my dwarf trees grew too tall for regulations and had to be trimmed, some to the point where the tree could not survive and then had to be cut down.
And - be aware that Switzerland's micro climates can have an impact on the robustness of fruit trees. Another reason I like the Haeberli site - they list whether a species is considered disease resistant or robust, as well as whether it is appropriate for 'Hohenlage'. I'm only at just under 800m, but because we are on the dark side I've learned I have to plant for higher elevations.
Good luck - may you enjoy your trees and the fruits of your labors.