“Constructive dismissal and non-payment of salary and accrued vacation pay (Greece)”

I am seeking legal advice regarding constructive dismissal and the non-payment of outstanding salary and accrued vacation pay under Greek labour law.
I was employed in Greece under a contract that allowed for a 24/7 operational framework, while in practice I worked remotely under stable working arrangements.
In a short period of time, the employer imposed a series of unilateral changes to essential working conditions without consultation or contractual amendment. These included a requirement to work 10 consecutive days instead of the established schedule, the withdrawal of previously granted public holidays, and a mandatory return-to-office policy that would have required relocation and caused a fundamental disruption to my private and family life. Employees were informed that failure to comply would result in termination.
As a result of the cumulative and materially detrimental impact of these measures, I submitted my resignation with immediate effect, expressly stating that it was not voluntary and that I considered the circumstances to constitute constructive dismissal. The employer acknowledged receipt of my resignation but disputes that the circumstances amount to constructive dismissal and subsequently asserted that I remain employed and must continue to perform my duties.
I have not returned to work and consider the employment relationship to have ended. Despite this, the employer has not paid my final salary or my accrued but unused vacation days.
I am seeking advice on (a) the strength of a constructive dismissal claim under Greek law, and (b) the appropriate legal steps to recover outstanding salary and accrued vacation pay.