Ishodad of Merv, in his commentaries on the gospels, quotes from Eusebius To Marinus. The commentaries were printed by Gibson in 1911 with an English translation. Vol. 1, p. 143 contains the Eusebius, on Mark 15. This is online in PDF here. The Syriac text is in vol. 2, here.
The other passage appears in the letters of Severus of Antioch, published in Syriac with English translation by E. W. Brooks in the Patrologia Orientalis 14, p. 270 (of the PDF). This is online here, and I transcribed the English here long ago.
The two passages seem to be on the same material. Probably neither actually had a full text of Eusebius before him, but relied on excerpts.