SUMMARY

Dolphin's konsole panel installed on a non-KDE system does not source $ZDOTDIR/.zshrc anymore.
In 20.04 it still works.
Konsole 20.08 does still source $ZDOTDIR/.zshrc correctly.
When sourcing $ZDOTDIR/.zshrc from the console panel in dolphin, it works correctly.
On a manjaro vm with kde fully installed and dolphin 20.08 as well as konsole 20.08 the problem remains the same: 
When $ZDOTDIR is set, konsole starts zsh correctly while dolphin doesn't.

When disabling restore and setting "Show on startup" to a fixed dir, the problem doesn't persist.

Possible duplicate of https://bugs.kde.org/show_bug.cgi?id=407990, although here it only applies to $ZDOTDIR and the issue did not exist in 20.04.

STEPS TO REPRODUCE
1. Set the profile used in dolphin konsole to zsh
2. create a .zshrc in e.g. .config/zsh/.zshrc  
3. Set $ZDOTDIR, either through konsoles environment variables or other methods like xprofile
4. open dolphin (after renewed login/reboot)
5. open konsole

OBSERVED RESULT
dolphin doesn't source the config correctly, konsole does

EXPECTED RESULT
both source the config correctly

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 5.19.4
KDE Frameworks Version: 5.73.0
Qt Version: 5.15.0

ADDITIONAL INFORMATION
zsh 5.8