I am working in ABC Systems (formerly known as DEF Systems before it was acquired by ABC Systems)
In the above one, don’t you think “formerly” or “before” is extra? Anyway the above sentence is grammatically correct, right? It conveys the meaning correctly, right? ABC systems acquired DEF Systems. The change in name is because of the acquisition. That’s what I am trying to say and I believe the above sentence conveys that.
You need to review the sentence before it can be deemed grammatically correct, as it contains errors before we reach the part in parentheses but there is no need to use both ‘formerly’ and ‘before it was acquired’ (though it is not wrong to do so).