When they say "running a datacenter" they almost certainly mean "buying servers to put into rented colocation space".
Just about anyone who has significant network connectivity has a footprint in an Equinix datacenter. In the Bay Area you want to be in Equinix SV1 or SV5, at 11, and 9 Great Oaks, San Jose.
If you're there, you can order a cross connect to basically any telco you can imagine, and any other large company. You can also get on the Equinix exchange and connect to many more.
But, Equinix charges you a huge premium for this, typically 2 - 3x other providers for space and power. Also they charge about $300 per month per cross connect.
So your network backbone tends to have a POP here, and maybe you put some CDN nodes here, but you don't build out significant compute. It's too expensive.
On the cheaper, but still highish quality end you have companies like CoreSite, and I'm pretty sure AWS has an entire building leased out at the CoreSite SantaClara campus for portions of us-west-1. (Pretty sure because people are always cagey about this kind of thing.)
I also know that Oracle cloud has been well know for taking lots of retail and wholesale datacenter space from the likes of CoreSite, and Digital Reality Trust, because it was faster to get to market. This is compared to purpose build datacenters, which is what the larger players typically do.
In the case of AWS, I know they generally do a leaseback, where they contract with another company who owns the building shell, and then AWS brings in all their own equipment.
But all these players are also going to have some footprint in various retail datacenters like Equinix and CoreSite for the connectivity, and some extra capacity.
Zoom is probably doing a mix of various colocation providers, and just getting the best deal / quality for the given local market they want to have a PoP in. Seems like they are also making Oracle Cloud part of that story.