Seems there are several affected services https://downdetector.com/
Slack: 16167 reports. Zoom: 224 reports. Google: 220 reports.
(And looking into it, indeed they are — looks like, in the detail view of a chart, there's a long-term weighted-running-average "baseline" value on the chart's data-points. See e.g. the dotted blue line on https://downdetector.com/status/google/. And the summary view seems to normalize its charts by their baseline.)