The two cases are not comparable at all. Howard Zinn's tome is a far-left distortion of history. What in the new curriculum could be considered to be extreme?
All accounts of history are distorted by the views of the person telling or writing it. The only difference between what Zinn is doing and what is done here is the political persuasion of the persons doing the distorting. The problem with both is that they want to dupe youth into believing that the version is the "true" version. But, you ask, what exactly is wrong with the Texas version. Let's evaluate some examples:
--Question the Founding Fathers' commitment to a purely secular government
Both the Texas position and the position of the article criticizing it are Half-truths. Some of the FFs were quite religious and saw America as founded on religious ideals. Others were areligious, deist, or otherwise non-Christian and resisted the idea of Christian spirituality in government. Others were from Christian minority groups (such as Baptists) and saw secularism as the best means of preserving religious liberty. The one thing that is clearly widley shared among the FFs was a commitment to religious liberty, both positively (the right to believe as you will) and negatively (the right to not be coerced by government to believe what you don't wish to believe). This is demonstrated by the very language of the 1st Amendment.
--Cover the Judeo-Christian influences of the nation's Founding Fathers, but not highlight the philosophical rationale for the separation of church and state.
Selective telling of history. Judeo-Christian influences are important, but so are secularist influences. To focus on one and not the other is a distortion of reality that promotes either an overly theocratic view of America's history or an over secularist view.
--Present Republican political philosophies and figures in a more positive light, including Joe McCarthy
If this charge is true, the criticism seems obvious. Both parties have had their successes and their blunders. McCarthyism is an obvious blunder in the view of anyone who believes that First Amendment is worth anything.
--Stress the superiority of American capitalism while eliminating the word "capitalism" from the text
Whether this is a "distortion" depends on your view of economics. Personally, I think that there is a lot good to be said about "American capitalism", not the least of which is that it is by no means true capitalism. Rather, what makes "American capitalism" great is that it is so heavily influenced by what is good about socialism without incorporating the evils of socialism. The only distortion I see here is to pretend that we live in an entirely "free market" system, rather than a regulated free market.
--Refer to the United States form of government as a "constitutional republic," rather than "democratic republic"
I have to give this one you. This doesn't strike me as that much of a distortion. We are a constitutional republic.
--Give Confederate president Jefferson Davis equal footing with Abraham Lincoln
I don't know what this means, so I cannot comment.
--Cut Thomas Jefferson from a list of figures whose writings inspired revolutions in the late 18th century and 19th century, replacing him with St. Thomas Aquinas and John Calvin (Jefferson is not well liked among conservatives on the board because he coined the term "separation between church and state")
Distortion in that it presents as influential those whose views most closely align with the ideologies of those presenting the history. To deny Jefferson's influence on revolutionary activity during the Enlightenment period is ignorant, if not outright dishonest. To suggest that Calvin and Aquinas were more influential in shaping this period of history is just wrong.
So, it is a mixed bag really. I could say the same about Howard Zinn. Frankly, I think it best to provide youth with more than one perspective on history so that they can sort through these things themselves. Most people end up accepting as truth a rough approximation of what they learned in school and those that don't go on to higher education often do not learn the art of critically evaluating what they are told. Critical analysis is a skill that is important for all people, regardless of what they end up doing with their career or how much education they have. Our schools should not be teaching kids to accept one biased version of reality without questioning it or comparing it to another perspective.