A key crossing inside Syria between an area held by the regime and one held by the opposition was closed again on Tuesday after violence followed its brief reopening this week. A local activist and a war monitor said that opposition groups protested the reopening of the Abu al-Zandin crossing in Aleppo province, which had been closed since 2020, and that it was twice hit by artillery shelling. A few trucks on Sunday moved through the crossing in what appeared to be a trial reopening. The move was met by protests and the crossing was hit by artillery shelling from an unknown source on Monday an…