So I answered the first blank with 漢字が簡単に書ける and the second one with 漢字を書くの.
My Japanese teacher, who is a native, told me that it should be 漢字が簡単 because this には functions as にとっては.
She then proceeded to say that the subject of potential verbs would normally be は (if I heard it correctly).
But I have seen countless sentences like 私にはできる and 私には分かる, which both mean the same as 私はできる and 私は分かる respectively (I think). So why is 書ける a big no no in this context? I feel like the second part of the sentence is saying 私たちにはそんなにできない.
I don't think my Japanese is good enough to ask her questions and understand her reply yet.