This is the 10719th most frequent Russian word.
восточнее
"East of" or "further east."
Here, 'восточнее' indicates relative geographic positioning to the east of another location.
Москва находится восточнее Санкт-Петербурга.
Moscow is located east of Saint Petersburg.
In this sentence, 'восточнее' is part of a comparative clause denoting regions located more to the east.
Чем восточнее регион, тем быстрее восходит солнце.
The further east the region, the earlier the sun rises.
The usage of 'восточнее' here specifies the position relative to a specific natural landmark.