Complex sentence: The diocese of Metz represents their territory, which was accordingly west of the Vosges, but Caesar makes the Mediomatrici extend to the Rhine, and consequently in his time they occupied the country between the Vosges and the Rhine.
Split into simpler sentences: The diocese of Metz represents their territory, which was accordingly west of the Vosges. But Caesar makes the Mediomatrici extend to the Rhine, and consequently they had in his time the country between the Vosges and the Rhine.