I loath the T and Z characters, so respectively I use a single dash (Between the date and time) and no Z; for time I often leave in the colons (:).

Example: 20210226-00:01:25 this presents the data in a format I can easily visually parse and also easily search for useful things in log files with.

When parsing such a date I tend to throw out all of the characters, but the 'Zulu' or timezone at the end probably should be parsed in anything that isn't a trivial internal use.