The latest version of the VMware virtual platform, vSphere 6.7, comes with exciting new features and improved capabilities that bring tremendous benefits for the network regarding improved functionality, management, security, and more that were not available in previous versions.
The entire upgrade process needs to follow a specific sequence and flow; first, all PSCs, then all vCenter Servers, then all ESXi hosts. However, if you have more VMware products, the entire sequence could be much more complicated.
For more information, see KB 53710: Update sequence for vSphere 6.7 and its compatible VMware products at https://kb.vmware.com/s/article/53710.