Left panels: locus of dynamical age Π = 1 at the redshift of image 1c (z = 3.237, top) and 12 (= 0.939, bottom) is highlighted with yellow contours; a star cluster with an effective radius matching one HST pixel (30 mas) lying within such contours is gravitationally bound if its age is larger than 3 Myr or it has a stellar mass larger than 2 × 10⁶ M_⊙. The compact knots detected in image 1c and 12 are candidate gravitationally-bound star clusters under the above assumptions. The insets show the zoomed source 1c and 12, with arrows indicating the most magnified knots. Right panel: same contours of Π = 1 at the redshift of source 1 adopting the HST 30 mas pix⁻¹ scale (cyan line), VLT/MAVIS (7.5 mas pix⁻¹, green line), and E-ELT/MAORY-MICADO (4 mas pix⁻¹, yellow line) are superimposed onto the same HST color image shown in the left panels (red = F105W, green = F814W and blue = F606W). The layout of the MDLF is shown in red. It is worth noting that ELT can probe gravitationally bound young massive clusters even with moderate magnification 2 <  μ <  4, a regime in which μ is free from systematic errors and by foreground contamination by galaxy cluster members.