Just to be clear, a password protected zip file should be an enormous blinking red light. 99% of the time, password protected zips are used to prevent virus scanners from scanning the content of the zip. Typically email providers like google will provide you with a warning that they have been unable to scan the file.
As for emails about contract jobs, even 15+ years ago these could be very targeted, specifying your company/resume etc. Now it will be getting even worse with chatGPT to write these emails in far less time and far more convincingly from non-native speakers.
Also note, unzipping files to look into them isn't automatically safe either... there are plenty of older CVEs where zip software had vulnerabilities allowing code execution, and a zero day is always possible. That's on top of the fact that zips can conceal file types of other software that might also have current CVEs.
Short story, and this should be followed by everyone in the tech community, never ever open attachments from anyone you don't know, and treat all attachments from people you do know as requiring scanning first. Not doing so puts your coworkers and your customers at risk. If you're accepting proposals for contract work, your process should always require one-on-one communication prior to accepting any attachments.