Where to Find and Catch Zekrom
From Pokemon Go Wiki
Zekrom are found and captured in Nest and Habitat locations.
Nests
Zekrom Nests are locations that consistently spawn Zekrom.
Habitats
Zekrom Habitats are spawn locations where Zekrom is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: