Morphology and photo-z of Zhúlóng. The left panel shows a 4″ × 4″ stacked image (F277W+F356W+F444W) with contour maps (start from 3σ). The top right panels show these same stamps in different filters. The central core’s SED (circled in red; measured in 0.16″ radius) has a clear post-starburst shape, which is shown in the middle right panels. In the middle right panels, the left one shows the EAZY SED fit together with the photometric points, and the right one shows the photometric redshift likelihood distribution, which has a single peak consistent with $z_{\mathrm{phot}}=5.2_{-0.2}^{+0.3}$. A neighboring star-forming clump (circled in blue) has a very robust redshift of $z_{\mathrm{phot}}=5.{15}_{-0.03}^{+0.04}$ from photometry due to strong emission lines.