* When Zoom is already installed:
- should be able to handle most instances
- needs to account for version management, eg installed version zoom could still be version that is too old to process the uri correctly. Version could be in the uri.
When Zoom is not installed:
- an information dialog needs to be somehow shown to the receiving user, asking them if they want to install 'Zoom'.
- that screen must include the 'uri' and validate certificates etc to prevent abuse (hence must necessarily be 'ugly' and not 'seamless')
- the language on that dialog has to be provided by the OS/Browser, not the software vendor, to prevent abuse. For similar reasons the Windows UAC dialog text can't be written by the vendor.
- the language employed by the OS/Browser has to of necessity be fairly neutral, neither encouraging nor discouraging installation, to prevent abuse. This is necessarily at odds with the UI principle of leading the inexperienced user through clear steps to achieve their intended goal.
- the user of average-to-lower-quartile experience, as of 2019, for a product with a client base of 40 million+, is likely not in a position to meaningfully distinguish a legitimate Zoom install uri from a malicious / imposter one. Hence any popular software using this install-from-uri-handler becomes an appealing target for malicious actors to mimic, which they will.
- some proportion of users will likely install from malicious links, and whichever product (let's say Zoom for example) is the most likely software for malicious actors to masquerade as will become the name associated with the attack in the mind of the wounded public
Secondly, version checks assume that the user wants to run this specific protocol handler. I as the user might prefer to run an open source non-official zoom client. I think the OS should only be trying to help me if I don't have any handler.