Computational chemistry software to generate files of cartesian coordinates and zmatrix of molecules
This is not the answer to your question, but it is a comment about an approach to the aims, based on the comments. If coding is an option, RDKit is a good option, specifically adding constraints (restraints) to the ForceField and optimising. Given a molecule:
from rdkit import Chem
from rdkit.Chem import AllChem

acetate = Chem.MolFromSmiles('CC(=O)C')

Normally the 3D conformer is generated with:
AllChem.EmbedMolecule(acetate)

And it stops there. However, then you can manually control the force field —either UFF (more elements) or MMFF (classic choice).
ff = AllChem.UFFGetMoleculeForceField(mol)
ff.Initialize()
print(ff.Minimize()) # this tells you if it failed.

Within this, you can add constraints, such as:
ff.AddDistanceConstraint(0, 1, 2., 2.1, 1_000_000_000)

Note that the weight needs to be set absurdly high for absurd lengths. To check it work you could do:
dm = Chem.Get3DDistanceMatrix(acetate)
print(f'{dm[0,1]} Å. {ff.CalcEnergy()} kcal/mol')