Table II. Individual contributions to the mass shift coefficient K (GHz · amu) for the 2 p$_{1}$$_{/}$$_{2}$ − 2 s and 2 p$_{3}$$_{/}$$_{2}$ − 2 s transitions in Li-like zinc (Z=30). SMS values from the related results by other nonrelativistic calculations, we estimate an uncertainty associated with the electron correlation as 0 . 05% for lithium, 0 . 002% for Li-like boron and much less for ions with larger nuclear charge numbers. One-electron and two-electron QED recoil corrections were calculated in accordance with our previous works [36, 37, 47]. The evaluation is performed for extended nuclei within the approximation of noninteracting electrons. The electron-electron interaction is suppressed by a factor 1 /Z , therefore we estimate the uncertainty of the QED recoil contribution mul- tiplying it by 1 /Z . As one can see, in the case of Li our values agree well with the previous theoretical predictions [35, 39–44] as well as with the experimental data [45, 46]. In Fig. 1 we plot the individual contributions to the MS coefficient K for the 2 p$_{1}$$_{/}$$_{2}$ − 2 s and 2 p$_{3}$$_{/}$$_{2}$ − 2 s transitions in Li-like ions. The dotted line indicates the relative contribution of the electron-electron interaction; the dashed line represents the relativistic correction; and the dashed-dotted line stands for the QED part of the coefficient. We observe that for low- Z ions it is extremely important to include the electron-electron interaction effects. 8 Subset 2 p$_{1}$$_{/}$$_{2}$ − 2 s 2 p$_{3}$$_{/}$$_{2}$ − 2 s Ref. MS operator -224600(3) -230073(3) -230161 nr -230161 nr -246954 hyd -253951 hyd NMS -21862.0 -34139.7 SMS -235922.0 -225509.0 RNMS 13807.8 22890.0 RSMS 19377.1 6685.8 QED -591(20) × 10 -560(20) × 10 1-el QED -5411 -5504 2-el QED -497 -98 Total theory -23051(20) × 10 -23568(20) × 10