Question

we looking forward to receiving your quotation. we look forward to your early reply.

什么时候look是ing的形式，什么时候不是？

Answer 1

原句应为we are looking forward to receiving your quotation , are looking forward to be looking forward to是现在进行时表将来 所以不能改为一般现在时 通常英语写信的话look forward to也用于现在进行时的 其实，就是现在进行时和一般现在时的差别。

i am looking forward to your reply 我正在盼望着你的答复
i look forward to your reply 我(经常或总是)盼望你的答复

Answer 2

第一句是错的，「we」和「looking」之间一定该有「are」
很简单的现代进行时