Thank you for this input.
Back to the title of the thread, how can an infinite universe be created from zero, zero being only a way of describing it right before the BB.
To simplify, let's consider only numbers.
Starting with zero, one can create an infinite quantity of numbers, 1, 2, 3, 100 and so on, as long as one also creates - 1, - 2, -3 , - 100 and so on, so that the sum total of the numbers created always remains equal to zero.
Such a creation is instantaneous, there was zero and in no time there is an infinite quantity of numbers.
Yet, as a whole nothing has really been created, as would have been the case if, say, only positive numbers had been created.
An observer can then find out that there is much more complexity than what appears at first sight, that these numbers can be manipulated, dissected, transformed in multiple ways, that one can start building equations with them, in the process discovering a whole (mathematical) universe.
Now, if the numbers were replaced with the energy and forces created with the BB, and that this energy and forces were then transformed into more and more complex things, yet cancelling each other on a global scale, an infinite universe could be created out of nothing, with its total content amounting to nothing.