Q.  This year (5781) when Shabbos Chazon was Erev Tisha Beav, after benching on Shaleshudes before the Shekia (sunset), can one still sing Zemiros of Shabbos?
A. There are different traditions. The more Litfishe (Lithuanian)and Yeshiva people would not. Yet it is a common practice by Chasidim to sing Zemiros until nightfall, and some even after.
Horav Shlomo Miller’s Shlit’a opinion is that Zemiros and tunes that are earnest and dedicated to seriously awake the service to Hashem are permitted
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a