Transition from the symbiotic nova outburst to quiescent phase and eventually to Z And-type outburst for AG Peg, V1329 Cyg, and V426 Sge. The sine curve fits the wave-like orbitally related variation. Panel a: descending part of the historical LC of AG Peg from its 1850 symbiotic nova outburst. The 2015 Z And-type outburst is shifted by −9 × P_orb for a better comparison. Data are from Meinunger (1983) and Sekeráš et al. (2019). Panel b: historical LC of V1329 Cyg covering its symbiotic nova outburst around 1965. Data were summarised by Chochol et al. (1999). Panel c: 1968 symbiotic nova outburst (m_pg in blue) and the 2018 Z And-type outburst (V in red) of V426 Sge. Data for the latter event are shifted by −18 × P_orb and +0.75 mag.