The optimization process and recommendations:

1. Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
2. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.

Optimal indexes for this query:

CREATE INDEX operdetails_idx_coper_cdetail ON OperDetails (coper,cdetail);
CREATE INDEX details_idx_ckd_nrec ON details (ckd,NREC);

The optimized query:

SELECT
        det.*,
        od1.T_EQ T_SHABLON_EQ,
        od1.T_NV T_SHABLON_NV,
        od1.T_PRIM T_SHABLON_PRIM,
        od2.T_EQ T_PRAVKA_EQ,
        od2.T_NV T_PRAVKA_NV,
        od2.T_PRIM T_PRAVKA_PRIM,
        od3.T_EQ T_VALCOV_EQ,
        od3.T_NV T_VALCOV_NV,
        od3.T_PRIM T_VALCOV_PRIM,
        od4.T_EQ T_REZKA2_EQ,
        od4.T_NV T_REZKA2_NV,
        od4.T_PRIM T_REZKA2_PRIM 
    FROM
        CMKNEW.details det 
    LEFT JOIN
        CMKNEW.OperDetails od1 
            ON det.nrec = od1.cdetail 
            AND 81 = od1.coper 
    LEFT JOIN
        CMKNEW.OperDetails od2 
            ON det.nrec = od2.cdetail 
            AND 82 = od2.coper 
    LEFT JOIN
        CMKNEW.OperDetails od3 
            ON det.nrec = od3.cdetail 
            AND 83 = od3.coper 
    LEFT JOIN
        CMKNEW.OperDetails od4 
            ON det.nrec = od4.cdetail 
            AND 84 = od4.coper 
    WHERE
        det.ckd = :CKD 
    ORDER BY
        det.NREC